#include <bits/stdc++.h>
using namespace std;
int main() {
  long long int n, x, y, i, k, sum = 0;
  string s;
  cin >> n >> x >> y;
  cin >> s;
  long long int a[x], b[y + 1];
  for (i = 0; i < x; i++) {
    a[i] = s[n - 1 - i] - 48;
    ;
  }
  for (i = 0; i <= y; i++) {
    if (i != y)
      b[i] = 0;
    else
      b[i] = 1;
  }
  for (i = 0; i <= y; i++) {
    if (a[i] != b[i]) sum++;
  }
  for (i = y + 1; i < x; i++) {
    if (a[i] != 0) sum++;
  }
  cout << sum;
}
