#include <bits/stdc++.h>   using namespace std;   const int N = 5e5 + 10;   long long n, ans, f[N], now, sum;   char s[N];   signed main() {     scanf( %lld , &n);     scanf( %s , s + 1);     for (long long i = 1; i <= n; i++) f[i] = n + 1;     for (long long i = n; i >= 1; i--) {       if (s[i] -  0 )         sum += f[++now] - i;       else {         while (now) f[now] = now + i, now--;       }       ans += sum;     }     printf( %lld n , ans);     return 0;   }   