#include <bits/stdc++.h>
using namespace std;
#define ff endl
#define lf "\n"
#define fi first
#define se second
#define _ << ' ' <<
#define all(x) begin(x),end(x)
#define rall(x) rbegin(x),rend(x)
#ifdef DEBUG
constexpr bool IS_DEBUG = 1;
#define infor(fmt, ...) do { print(stderr, fmt, ##__VA_ARGS__); } while(0)
#define infof(fmt, ...) do { println(stderr, fmt, ##__VA_ARGS__); } while(0)
#else
constexpr bool IS_DEBUG = 0;
#define infor(fmt, ...)
#define infof(fmt, ...)
#endif
using ll = long long;
using pll = pair<ll, ll>;
using pii = pair<int, int>;
template<typename... Args>
using vec = vector<Args...>;
constexpr int LOG = 20;
constexpr int MOD = 1e9+7;
constexpr int MAXN = 1e5+7;
mt19937 timmy_loves_gambling(73);
long long count_triples(vector<int> H) {
const int N = H.size();
ll ans = 0;
auto check_triple = [&](int i, int j, int k) -> bool {
if(i < 0 || i >= N) return 0;
if(j < 0 || j >= N) return 0;
if(k < 0 || k >= N) return 0;
if(i >= j || j >= k) return 0;
vec<int> d = {j - i, k - j, k - i};
vec<int> h = {H[i], H[j], H[k]};
sort(all(d));
sort(all(h));
bool ok = d == h;
infof("... check_triple({}, {}, {}) -> {}", i, j, k, (int)ok);
return ok;
};
auto strip = [&](vec<int> &V) -> void {
sort(all(V));
V.resize(unique(all(V)) - V.begin());
};
for(int i = 0; i < N; ++i) {
int k = i + H[i];
if(k < 0 || k >= N) continue;
vec<int> J = {H[k] + i, k - H[k]};
strip(J);
for(auto j: J) {
ans += check_triple(i, j, k);
}
}
for(int i = 0; i < N; ++i) {
int j = i + H[i];
if(j < 0 || j >= N) continue;
ans += check_triple(i, j, i + H[j]);
}
for(int j = 0; j < N; ++j) {
int i = j - H[j];
if(i < 0 || i >= N) continue;
ans += check_triple(i, j, j + H[i]);
}
return ans;
}
vector<int> construct_range(int M, int K) {
assert(0 && "construct_range: unimplemented");
}
#ifdef LOCAL
namespace {
void run_part1() {
int N;
assert(1 == scanf("%d", &N));
std::vector<int> H(N);
for (int i = 0; i < N; i++)
assert(1 == scanf("%d", &H[i]));
fclose(stdin);
long long T = count_triples(H);
printf("%lld\n", T);
fclose(stdout);
}
void run_part2() {
int M, K;
assert(2 == scanf("%d %d", &M, &K));
fclose(stdin);
std::vector<int> H = construct_range(M, K);
int N = H.size();
printf("%d\n", N);
for (int i = 0; i < N; i++)
printf("%d%c", H[i], " \n"[i + 1 == N]);
fclose(stdout);
}
} // namespace
int main() {
int part;
assert(1 == scanf("%d", &part));
if (part == 1)
run_part1();
else if (part == 2)
run_part2();
return 0;
}
#endif
