/*
* Author: Nonoze
* Created: Saturday 27/07/2024
*/
#include <bits/stdc++.h>
using namespace std;
namespace std {
// https://judge.yosupo.jp/submission/193613
struct IOPre {
static constexpr int TEN = 10, SZ = TEN * TEN * TEN * TEN;
std::array<char, 4 * SZ> num;
constexpr IOPre() : num{} {
for (int i = 0; i < SZ; i++) for (int n = i, j = 3; j >= 0; j--) num[i * 4 + j] = n % TEN + '0', n /= TEN;
}
};
struct IO {
#if !HAVE_DECL_FREAD_UNLOCKED
#define fread_unlocked fread
#endif
#if !HAVE_DECL_FWRITE_UNLOCKED
#define fwrite_unlocked fwrite
#endif
static constexpr int SZ = 1 << 17, LEN = 32, TEN = 10, HUNDRED = TEN * TEN,
THOUSAND = HUNDRED * TEN, TENTHOUSAND = THOUSAND * TEN,
MAGIC_MULTIPLY = 205, MAGIC_SHIFT = 11, MASK = 15,
TWELVE = 12, SIXTEEN = 16;
static constexpr IOPre io_pre = {};
std::array<char, SZ> input_buffer, output_buffer;
int input_ptr_left, input_ptr_right, output_ptr_right;
IO() : input_buffer{}, output_buffer{}, input_ptr_left{}, input_ptr_right{}, output_ptr_right{} {}
IO(const IO&) = delete;
IO(IO&&) = delete;
IO& operator=(const IO&) = delete;
IO& operator=(IO&&) = delete;
~IO() { flush(); }
template<typename T> static constexpr bool is_char_v = std::is_same_v<T, char>;
template<typename T> static constexpr bool is_bool_v = std::is_same_v<T, bool>;
template<typename T> static constexpr bool is_string_v =
std::is_same_v<T, std::string> || std::is_same_v<T, const char*> ||
std::is_same_v<T, char*> || std::is_same_v< std::decay_t<T>, char*>;
template<typename T> static constexpr bool is_default_v =
is_char_v<T> || is_bool_v<T> || is_string_v<T> || std::is_integral_v<T>;
inline void load() {
memmove(std::begin(input_buffer),
std::begin(input_buffer) + input_ptr_left,
input_ptr_right - input_ptr_left);
input_ptr_right =
input_ptr_right - input_ptr_left +
fread_unlocked(
std::begin(input_buffer) + input_ptr_right - input_ptr_left, 1,
SZ - input_ptr_right + input_ptr_left, stdin);
input_ptr_left = 0;
}
inline void read_char(char& c) {
if (input_ptr_left + LEN > input_ptr_right) load();
c = input_buffer[input_ptr_left++];
}
inline void read_string(std::string& x) {
char c;
while (read_char(c), c < '!') continue;
x = c;
while (read_char(c), c >= '!') x += c;
}
template<typename T>
inline std::enable_if_t<std::is_integral_v<T>, void> read_int(T& x) {
if (input_ptr_left + LEN > input_ptr_right) load();
char c = 0;
do c = input_buffer[input_ptr_left++];
while (c < '-');
[[maybe_unused]] bool minus = false;
if constexpr (std::is_signed<T>::value == true)
if (c == '-') minus = true, c = input_buffer[input_ptr_left++];
x = 0;
while (c >= '0')
x = x * TEN + (c & MASK), c = input_buffer[input_ptr_left++];
if constexpr (std::is_signed<T>::value == true)
if (minus) x = -x;
}
inline void skip_space() {
if (input_ptr_left + LEN > input_ptr_right) load();
while (input_buffer[input_ptr_left] <= ' ') input_ptr_left++;
}
inline void flush() {
fwrite_unlocked(std::begin(output_buffer), 1, output_ptr_right, stdout);
output_ptr_right = 0;
}
inline void write_char(char c) {
if (output_ptr_right > SZ - LEN) flush();
output_buffer[output_ptr_right++] = c;
}
inline void write_bool(bool b) {
if (output_ptr_right > SZ - LEN) flush();
output_buffer[output_ptr_right++] = b ? '1' : '0';
}
inline void write_string(const std::string& s) {
for (auto x : s) write_char(x);
}
inline void write_string(const char* s) {
while (*s) write_char(*s++);
}
inline void write_string(char* s) {
while (*s) write_char(*s++);
}
template <typename T>
inline std::enable_if_t< std::is_integral_v<T>, void> write_int(T x) {
if (output_ptr_right > SZ - LEN) flush();
if (!x) {
output_buffer[output_ptr_right++] = '0';
return;
}
if constexpr (std::is_signed_v<T>) if (x < 0) output_buffer[output_ptr_right++] = '-', x = -x;
int i = TWELVE;
std::array<char, SIXTEEN> buf{};
for (; x >= TENTHOUSAND; x /= TENTHOUSAND, i -= 4)
memcpy(std::begin(buf) + i, std::begin(io_pre.num) + (x % TENTHOUSAND) * 4, 4);
if (x < HUNDRED) {
if (x < TEN) output_buffer[output_ptr_right++] = '0' + x;
else {
uint32_t q = (uint32_t(x) * MAGIC_MULTIPLY) >> MAGIC_SHIFT;
uint32_t r = uint32_t(x) - q * TEN;
output_buffer[output_ptr_right++] = '0' + q;
output_buffer[output_ptr_right++] = '0' + r;
}
} else {
if (x < THOUSAND)
memcpy(std::begin(output_buffer) + output_ptr_right, std::begin(io_pre.num) + (x << 2) + 1, 3),
output_ptr_right += 3;
else
memcpy(std::begin(output_buffer) + output_ptr_right, std::begin(io_pre.num) + (x << 2), 4),
output_ptr_right += 4;
}
memcpy(std::begin(output_buffer) + output_ptr_right, std::begin(buf) + i + 4, TWELVE - i);
output_ptr_right += TWELVE - i;
}
template <typename T_>
std::enable_if_t<(is_default_v< std::remove_cv_t< std::remove_reference_t<T_> > >), IO&> operator<<(T_&& x) {
using T = std::remove_cv_t< std::remove_reference_t<T_> >;
if constexpr (is_bool_v<T>) write_bool(x);
else if constexpr (is_string_v<T>) write_string(x);
else if constexpr (is_char_v<T>) write_char(x);
else if constexpr (std::is_integral_v<T>) write_int(x);
return *this;
}
template<typename T>
std::enable_if_t<(is_default_v<T> && !is_bool_v<T>), IO&> operator>>(T& x) {
if constexpr (is_string_v<T>) read_string(x);
else if constexpr (is_char_v<T>) read_char(x);
else if constexpr (std::is_integral_v<T>) read_int(x);
return *this;
}
IO* tie(std::nullptr_t) { return this; }
void sync_with_stdio(bool) {}
} io;
} // namespace std
using std::io;
#define cin io
#define cout io
#ifndef _IN_LOCAL
#define dbg(...)
#endif
#define endl '\n'
#define endlfl '\n' << flush
#define quit(x) return (void)(cout << x << endl)
template<typename T> void read(T& x, bool write=0, bool write2=1) { if (write && write2) cout << x << endl; else if (write) cout << x << ' '; else cin >> x;}
template<typename T1, typename T2> void read(pair<T1, T2>& p, bool write=0, bool write2=1) { read(p.first, write, 0), read(p.second, write, 0); if (write && write2) cout << endl;}
template<typename T> void read(vector<T>& v, bool write=0) { for (auto& x : v) read(x, write, 0); if (write) cout << endl; }
template<typename T1, typename T2> void read(T1& x, T2& y, bool write=0) { read(x, write), read(y, write); if (write) cout << endl; }
template<typename T1, typename T2, typename T3> void read(T1& x, T2& y, T3& z, bool write=0) { read(x, write), read(y, write), read(z, write); if (write) cout << endl; }
template<typename T1, typename T2, typename T3, typename T4> void read(T1& x, T2& y, T3& z, T4& zz, bool write=0) { read(x, write), read(y, write), read(z, write), read(zz, write); if (write) cout << endl; }
template<typename T> void print(T x) { read(x, 1); }
template<typename T1, typename T2> void print(T1 x, T2 y) { read(x, y, 1); }
template<typename T1, typename T2, typename T3> void print(T1 x, T2 y, T3 z) { read(x, y, z, 1); }
template<typename T1, typename T2, typename T3, typename T4> void print(T1 x, T2 y, T3 z, T4 zz) { read(x, y, z, zz, 1); }
#define sz(x) (int)(x.size())
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
#define pb push_back
#define mp make_pair
#define fi first
#define se second
#define cmin(a, b) a = min(a, b)
#define cmax(a, b) a = max(a, b)
#define int long long
const int inf = numeric_limits<int>::max() / 4;
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
const int MOD = 1e9+7, LOG=25;
void solve();
signed main() {
ios::sync_with_stdio(0);
cin.tie(0);
int tt=1;
// cin >> tt;
while(tt--) solve();
return 0;
}
struct SegTree {
int n;
vector<int> t;
SegTree(int _n) {
n=_n;
t.resize(4*n);
}
void update(int x, int val, int node=1, int l=0, int r=-1) { if (r==-1) r=n-1;
if (l>x || r<x) return;
if (l==r) {
t[node]=val;
return;
}
int mid=(l+r)/2;
update(x, val, node*2, l, mid);
update(x, val, node*2+1, mid+1, r);
t[node]=max(t[node*2], t[node*2+1]);
}
int query(int x, int node=1, int l=0, int r=-1) { if (r==-1) r=n-1;
if (l>x) return 0;
if (r<=x) return t[node];
int mid=(l+r)/2;
int s1=query(x, node*2, l, mid);
int s2=query(x, node*2+1, mid+1, r);
return max(s1, s2);
}
};
int n, k, m, q;
vector<pair<int, int>> a;
void solve() {
read(n);
a.clear(), a.resize(n); read(a);
for (int i=0; i<n; i++) a[i].fi=i-a[i].fi-1, a[i].se+=i+1;
SegTree st(n);
vector<vector<int>> toadd(2*n+1);
vector<int> ans(n);
for (int i=0; i<n; i++) {
toadd[a[i].se].pb(i);
for (auto u: toadd[i]) st.update(u, ans[u]);
ans[i]=st.query(a[i].fi)+1;
}
cout << *max_element(all(ans)) << endl;
}
