#include <iostream>
#include <string>
using namespace std;

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

    int N;
    string S;
    cin >> N >> S;

    long long ret = 0;
    long long last0 = -1;
    for (long long i = 1; i < N; ++i) {
        if (S[i] == '0') {
            ret += i * (N - i);
            if (last0 >= 0) ret -= last0 * (N - i);

            last0 = i;
        }
    }
    cout << ret << endl;
}