#include <iostream>
#include <cmath>
#include <unordered_map>
#include <map>
#include <set>
#include <queue>
#include <vector>
#include <string>
#include <iomanip>
#include <algorithm>
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
using namespace std;
typedef long long ll;
ll linf = 1e15+1;
inline void scoobydoobydoo(){
ios::sync_with_stdio(false);
ios_base::sync_with_stdio(false);
cin.tie(NULL); cout.tie(NULL);
}
set<int> bals[1000003];
int main(){
scoobydoobydoo();
int n; cin >> n;
set<pair<int, int>> v;
for (int i = 0; i < n; i++){
int h; cin >> h;
v.insert({i, h});
bals[h].insert(i);
}
int sum = 0;
while (!v.empty()){
sum++;
int h = (*v.begin()).second;
int i = (*v.begin()).first;
v.erase(v.begin());
if (v.empty())break;
if (bals[h-1].empty())break;
auto it = bals[h-1].upper_bound(i);
while (h >= 1 && it != bals[h-1].end()){
auto itr = v.find({*it, h-1});
v.erase(itr);
bals[h-1].erase(it);
i = *it;
h--;
if (bals[h-1].empty())break;
it = bals[h-1].upper_bound(i);
}
}
cout << sum << endl;
return 0;
}
