#define _USE_MATH_DEFINES
#define _CRT_SECURE_NO_WARNINGS
#include "bits/stdc++.h"
#define rep(i,n) for(int i = 0;i < n;i++)
#define P(p) cout<<(p)<<endl;
#define pi 3.1415926535
using namespace std;
typedef long long ll;
int dx[] = { 0, 1, 0, -1 };
int dy[] = { -1, 0, 1, 0 };

unsigned long long sttoi(std::string str) {
	unsigned long long ret;
	std::stringstream ss; ss << str;
	ss >> ret;
	return ret;
}

ll gcd(ll a, ll b){
	if (b > a)swap(a, b); if (b == 0)return a; else{ return gcd(b, a%b); }
}

void solve() {
	int v[1000];
	int sum = 0;
	int n;
	cin >> n;
	fill(v, v + 1000, 0);
	for (int i = 1; i <= n;i++){
		cin >> v[i];
		sum += v[i];
	}
	int top;
	int s = 1;
	if (s == sum){
		top == 1;
	}
	else{
		for (int i = 1;; i++){
			if (s + 2 * i + 1 <= sum){
				top = i + 1;
				s += 2 * i + 1;
			}
			else{
				break;
			}
		}
	}
	int height[10000];
	fill(height, height + 10000, 0);
	for (int i = 1; i <= top;i++){
		height[i] = i;
		height[i + (top - i) * 2] = i;
	}
	int need = 0;
	int left = 0;
	for (int i = 1; i <= n; i++){
		int gap = v[i] - height[i];
		if (gap < 0){
			need += gap;
		}
		else{
			left += gap;
		}
	}
	P(left);
}

int main() {
	solve();
	return 0;
}