#include<iostream>
#include<vector>
#include<cmath>
#include<algorithm>
using namespace std;
int main(){
	int n;	cin >> n;
	vector<int> a(n);
	int sum = 0;
	for (int i = 0; i<n; i++){
		cin >> a[i];
		sum += a[i];
	}
	sum = (int)sqrt(sum);
	int ans = 0;
	int now = 0;
	for (int i = 0; i<n; i++){
		if (i<sum)	now++;
		else if (now>0)	now--;
		ans += max(0, a[i] - now);
	}
	cout << ans << endl;
	return 0;
}