#include <bits/stdc++.h>   using namespace std;   int main() {     long long int k, i, cn = 0, cnt = 0, j;     cin >> k;     string s;     cin >> s;     map<long long int, long long int> ans;     long long int a[s.length()], n = s.length();     for (i = 0; i < s.length(); i++) {       if (s[i] ==  1 ) cnt++;     }     if (k > cnt)       cout <<  0  << endl;     else {       a[0] = (s[0] -  0 );       for (i = 1; i < s.length(); i++) {         a[i] = a[i - 1] + (s[i] -  0 );       }       i = 0;       j = 0;       ans[0] = 1;       for (i = 0; i < n; i++) {         if (a[i] >= k) cn += ans[a[i] - k];         ans[a[i]]++;       }       cout << cn << endl;     }   }   