#include <bits/stdc++.h>
using namespace std;
char str[300000], str2[300000];
int main() {
  int n, x, y;
  scanf("%d%d%d", &n, &x, &y);
  scanf("%s", str);
  int len = strlen(str);
  strcpy(str2, str);
  int count_ = 0;
  for (int i = len - 1; i >= len - y; i--) {
    if (str2[i] != '0') count_++;
  }
  if (str2[len - y - 1] != '1') count_++;
  for (int i = len - x; i < len - y - 1; i++) {
    if (str[i] != '0') count_++;
  }
  printf("%d\n", count_);
  return 0;
}
