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

int main(){
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);

    int N; cin >> N;
    vector<int> A(N);
    int suma = 0;
    for(auto &a : A) cin >> a,suma += a;
    A.resize(209);
    int answer = 1001001001;
    for(int i=1; i<=104; i++){
        int h = 0,dh = 1,now = 0,use = 0;
        for(int k=0; k<209; k++){
            if(h == i) dh *= -1;
            h += dh,h = max(h,0);
            use += h;
            now += max(0,A.at(k)-h);
        }
        if(use > suma) break;
        answer = min(answer,now);
    }
    cout << answer << endl;
}