#include <bits/stdc++.h>
using namespace std;
const int maxn = 2e5 + 10;
const int mod = 998244353;
int a[maxn];
int main() {
  int n, x, y;
  cin >> n >> x >> y;
  string ss;
  cin >> ss;
  reverse(ss.begin(), ss.end());
  int t = 0;
  for (int i = 0; i < x; i++) {
    if (i == y) {
      if (ss[i] == '0') t++;
    } else {
      if (ss[i] == '1') t++;
    }
  }
  cout << t << endl;
}
