#include <bits/stdc++.h>
using namespace std;
int main(void) {
  char A[250000];
  char B[250000];
  int n, x, y, i;
  int count = 0;
  cin >> n >> x >> y;
  for (i = 0; i < n; i++) scanf(" %c", &A[i]);
  for (i = n - 1; i >= 0; i--) B[(n - 1) - i] = A[i];
  for (i = 0; i < x; i++) {
    if (i == y) {
      if (B[i] == '0') count++;
    } else {
      if (B[i] == '1') count++;
    }
  }
  cout << count;
}
