#include <bits/stdc++.h>
using namespace std;
int main() {
  long long n, x, y, t = 0, i, u = 0;
  char a[1000009];
  cin >> n >> x >> y;
  cin >> a;
  for (i = n - 1 - x + 1; i <= n - 1 - y - 1; i++) {
    if (a[i] == '1') t++;
  }
  if (a[n - 1 - y] == '0') t++;
  for (i = n - 1 - y + 1; i <= n - 1; i++)
    if (a[i] == '1') t++;
  cout << t << endl;
}
