#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, x, y, i;
  cin >> n >> x >> y;
  string s;
  int ans = 0;
  cin >> s;
  for (i = n - 1; i >= 0; i--) {
    if (n - i - 1 == x) {
      break;
    } else if (n - i - 1 == y) {
      if (s[i] == '0') {
        ans++;
      }
    } else {
      if (s[i] == '1') ans++;
    }
  }
  cout << ans;
  return 0;
}
