#include <iostream>
#include <vector>
#include <algorithm>
#include <iomanip>
#include <string>
#include <stack>
#include <queue>
#include <map>
#include <set>
#include <tuple>
#include <cstdio>
#include <cstdlib>
#include <cmath>
#include <climits>
#include <cassert>
#include <cstdint>
#include <numeric>
#include <bitset>
#include <functional>

using namespace std;

using ll =  long long;
using Pll = pair<ll, ll>;
using Pii = pair<int, int>;

constexpr ll MOD = 1000000007;
constexpr long double EPS = 1e-10;
constexpr int dyx[4][2] = {
    { 0, 1}, {-1, 0}, {0,-1}, {1, 0}
};

int main() {
    ios::sync_with_stdio(false); cin.tie(nullptr);
    int n;
    cin >> n;
    vector<int> b(n);
    vector<int> non_zero;
    for(int i=0;i<n;++i){
        cin >> b[i];
        if(b[i]) non_zero.push_back(i);
    }

    
    int non_zero_i = 0;
    ll ans = 0LL;
    for(int i=0;i<n;++i) {
        if(b[i] == 0) {
            ans += abs(non_zero[non_zero_i] - i);
            --b[non_zero[non_zero_i]];
            b[i] = 1;
            if(b[non_zero[non_zero_i]] == 0) ++non_zero_i;
        }
    }
    cout << ans << endl;

}