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

int main()
{
    int N;
    cin >> N;
    vector<pair<int,int>> cnt;
    vector<int> flag;
    for(int i = 0; i < N; i++)
    {
        int b;
        scanf("%d", &b);
        if(b == 0) flag.push_back(i);
        else if(b >= 2) cnt.push_back(make_pair(i, b-1));
    }

    long long ans = 0;
    for(int i = 0; i < flag.size(); i++)
    {
        int idx = flag[i];
        int jdx = 0;
        int minv = 1e8;
        for(int j = 0; j < cnt.size(); j++)
        {
            int c1 = cnt[j].first;
            int c2 = cnt[j].second;
            if(abs(idx-c1) < minv && c2 > 0)
            {
                jdx = c1;
                minv = abs(idx-c1);
            }
        }
        cnt[jdx].second -= 1;
        ans += (long long)minv;
    }

    cout << ans << endl;
    return 0;
}