#include <bits/stdc++.h>
using namespace std;
using ll = long long;
constexpr int N = 1e6+5;
int n, a[N];
int main() {
ios_base::sync_with_stdio(false);
cin.tie(0);
cin >> n;
priority_queue<pair<int,int>> pq;
for(int i = 0; i < n; i++) {
cin >> a[i];
pq.push(make_pair(a[i], i));
}
int c = 0;
vector<bool> vis(n, 0);
while(!pq.empty()) {
int pos = pq.top().second;
pq.pop();
if(vis[pos]) {
continue;
}
int cur = a[pos];
for(int i = pos; i < n; i++) {
if(!vis[i] && a[i] == cur) {
vis[i] = 1;
cur--;
}
}
c++;
}
cout << c;
return 0;
}
