#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, x, y;
  while (scanf("%d %d %d", &n, &x, &y) == 3) {
    string s;
    cin >> s;
    int l = s.length();
    int p = x, q = y, j = 0;
    for (int i = l - 1; i >= 0 && p--; i--) {
      if (s[i] == '1') j++;
    }
    if (s[l - y - 1] == '1')
      j--;
    else
      j++;
    cout << j << endl;
  }
}
