#include <bits/stdc++.h>
using namespace std;
int main(void) {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  long long n, m, l, mx = 0, sum = 0, tired, x, y, ans = 0;
  cin >> n >> x >> y;
  string s;
  cin >> s;
  reverse(s.begin(), s.end());
  for (int i = 0; i < x; i++) {
    if (i == y) {
      if (s[i] == '0') {
        ans++;
      }
    } else if (s[i] == '1') {
      ans++;
    }
  }
  cout << ans;
}
