#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ld = long double;
using pii = pair<int, int>;
using pll = pair<long long, long long>;
using ull = unsigned long long;
#ifdef HAMED
#define DB 1
#else
#define DB 0
#endif
#define debug if(DB) cout
#define X first
#define Y second
#define SZ(x) int(x.size())
#define all(x) x.begin(), x.end()
#define mins(a,b) (a = min(a,b))
#define maxs(a,b) (a = max(a,b))
#define Mp make_pair
#define lc id<<1
#define rc lc|1
#define mid ((l+r)>>1)
mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count());
const ll INF = 1e9 + 23;
const ll MOD = 1e9 + 7;
const int MXN = 1e6 + 5;
const int LOG = 23;
int c[MXN], ans, n;
void Main() {
cin >> n;
for(int i=1; i<=n; i++) {
int a;
cin >> a;
if(c[a+1]) {
c[a+1]--;
c[a]++;
}
else {
c[a]++;
ans++;
}
}
cout << ans << '\n';
}
int32_t main() {
cin.tie(0); cout.tie(0); ios_base::sync_with_stdio(0);
int T = 1;
// cin >> T;
while(T--) Main();
return 0;
}
