#include <bits/stdc++.h>
#define F first
#define S second
#define PB push_back
#define MP make_pair
#define dbg(x) cerr << #x << " = " << x << "\n"
#define fast_io ios_base::sync_with_stdio(0); cin.tie(0); cout.tie()
using namespace std;
using ll = long long;
using ld = long double;
const int N = int(1e6) + 500;
int n, ans = 0;
int cnt[N];
int main() {
fast_io;
cin >> n;
for (int i = 0; i < n; ++i) {
int x;
cin >> x;
if (cnt[x] > 0) {
--cnt[x];
++cnt[x - 1];
continue;
}
++ans;
++cnt[x - 1];
}
cout << ans << "\n";
}
