#include<bits/stdc++.h>
using namespace std;
using ll = long long;

#define FOR(i,a,b) for(ll i=(a);i<(b);++i)
#define ALL(v) (v).begin(), (v).end()
#define p(s) cout<<(s)<<endl
#define p2(s, t) cout << (s) << " " << (t) << endl
#define br() p("")
#define pn(s) cout << (#s) << " " << (s) << endl
#define p_yes() p("Yes")
#define p_no() p("No")

const ll mod = 1e9 + 7;
const ll inf = 1e18;

int main(){
    cin.tie(0);
    ios::sync_with_stdio(false);

    // input
    ll N;
    cin >> N;

    vector<ll> A(N);
    FOR(i, 0, N){
        cin >> A.at(i);
    }

    ll sum = 0;
    for(ll a : A){
        sum += a;
    }

    // highest
    ll h = sqrt(sum);

    ll move = 0;
    FOR(i, 0, N){
        ll t; // target height
        if(i<h){
            t = i+1;
        }else{
            t = max(2*h-i-1, 0LL);
        }
        if(A[i]>t){
            move += A[i]-t;
        }
    }

    p(move);
    
    return 0;
}