#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, i, x, y, count = 0;
  cin >> n >> x >> y;
  char s[200001];
  cin >> s;
  for (i = n - x; s[i] != '\0'; i++) {
    if (i != n - y - 1 && s[i] == '1') count++;
    if (i == n - y - 1 && s[i] == '0') count++;
  }
  cout << count;
}
