#include <bits/stdc++.h>
int main() {
  int n, x, y, i, j, c = 0, d;
  scanf("%d%d%d", &n, &x, &y);
  char str[n];
  scanf("%s", str);
  for (i = n - 1; i > n - 1 - x; i--) {
    if (str[i] == '0' && i == (n - 1 - y)) {
      c++;
    } else if (str[i] == '1' && i != (n - 1 - y))
      c++;
  }
  printf("%d", c);
}
