#include <bits/stdc++.h>
using namespace std;
int mark1[1000000];
int mark[1000000];
int main() {
  string s;
  long long i, n, m, l, c = 0, x;
  cin >> l >> n >> m >> s;
  x = l - m - 1;
  for (i = l - n; i < l; i++) {
    if (i == x) {
      if (s[i] == '0') c++;
    } else if (s[i] == '1')
      c++;
  }
  cout << c << endl;
}
