#include <cstdio>
#include <cstdlib>
#include <iostream>
#include <string>
#include <cmath>
#include <algorithm>
#include <vector>
#include <queue>
#include <stack>
#include <map>

using namespace std;

int main(){
    int num[101],jou[101],n,ans=0,sum=0,retu,zou=0,sute=0;
    
    scanf("%d",&n);
    
    for(int i=1;i<=n;i++){
        scanf("%d",&num[i]);
        sum+=num[i];
    }
    
    for(int i=1;i<=100;i++)
        jou[i]=i*i;
    
    for(retu=1;;retu++){
        if(jou[retu]>sum)
            break;
    }
    
    retu=(retu-1)*2-1;
    
    for(int i=1;i<=retu;i++){
        if(i<=retu/2+(retu%2)){
            zou+=max(num[i]-i,0);
        }
        else{
            zou+=max(num[i]-(retu-i+1),0);
        }
    }
    
    
    for(int i=retu+1;i<=n;i++){
        sute+=num[i];
    }
    
        ans=zou+sute;
    
    printf("%d\n",ans);
    
    return 0;
}