#include <iostream>
#include <cstdio>
#include <cstring>
#include <vector>
#include <deque>
#include <queue>
#include <array>
#include <set>
#include <map>
#include <cmath>
#include <complex>
#include <algorithm>
#include <numeric>
#include <utility>
#include <tuple>
#include <functional>
#include <bitset>
#include <cstdint>
#include <cassert>
#include <random>

using namespace std;
using i64 = int64_t;
using i32 = int32_t;

int absi(int x) {
    return max(x, -x);
}
int main() {
    int n;
    cin >> n;
    vector<int> b(n);
    for (int i = 0; i < n; ++i) {
        cin >> b[i];
    }
    i64 ans = 0;
    for (int i = 0, j = 0; i < n && j < n; ) {
        while (i < n && b[i] > 0) ++i;
        while (j < n && b[j] < 2) ++j;
        if (i < n && j < n) {
            b[j]--;
            b[i]++;
            ans += absi(i - j);
        }
    }
    for (int i = 0; i < n; ++i) {
        assert(b[i] == 1);
    }
    cout << ans << endl;
    return 0;
}