#include "bits/stdc++.h"
#define REP(i, n) for(int i = 0; i < int(n); i++)
#define FOR(i,n,m) for(int i = int(n); i < int(m); i++)
using namespace std;
typedef long long ll;
const int MOD = 1e9 + 7;
const int INF = 1e9 + 6;
const ll LLINF = 1e18 + 1;

int main() {
    int n; cin >> n;
    vector<pair<int, int>> deq;
    vector<int> b(n);
    REP(i, n) {
        cin >> b[i];
        if (b[i] > 1) deq.push_back({i,b[i]});//idx,count
    }
    ll ans = 0;
    int now = 0;
    REP(i, n) {
        if (b[i] == 0) {
            ans += abs(deq[now].first - i);
            deq[now].second--;
            if (deq[now].second == 1) now++;
        }
    }
    cout << ans << endl;
    return 0;
}