#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  int n, x, y, cnt = 0;
  cin >> n >> x >> y;
  string s;
  cin >> s;
  for (int i = n - 1; x; i--) {
    if (i == (n - y - 1) && s[i] == '0')
      cnt++;
    else if (i == (n - y - 1) && s[i] == '1') {
    } else if (s[i] == '1')
      cnt++;
    x--;
  }
  cout << cnt;
}
