#include <bits/stdc++.h>
using namespace std;
void input(int n, int a[]) {
  for (int i = 0; i < n; ++i) cin >> a[i];
}
long long bin_expo(long long A, long long B, long long M) {
  long long res = 1LL;
  while (B > 0) {
    if (B % 2 == 1) {
      res = (res * A) % M;
    }
    A = (A * A) % M;
    B = B / 2;
  }
  return res;
}
int main() {
  long long n, x, y;
  cin >> n >> x >> y;
  string s;
  cin >> s;
  int ind = s.length() - 1;
  int cnt = 0;
  for (int i = 0; i < y; i++) {
    if (s[ind] == '1') {
      cnt++;
      s[ind] = '0';
    }
    ind--;
  }
  if (s[ind] == '0') {
    cnt++;
    s[ind] = '1';
  }
  int cc = 0;
  int idx = s.length() - 1;
  for (int i = 0; i < x; i++) {
    if (s[idx] == '1' && idx < ind) cc++;
    idx--;
  }
  cout << cc + cnt << endl;
  return 0;
}
