#include <bits/stdc++.h>
using namespace std;
const long long INF = 1e12, N = 3e5 + 100;
long long n, m, x, y;
long long b[N], g[N];
string ss;
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  cin >> n >> x >> y >> ss;
  reverse(ss.begin(), ss.end());
  for (long long i = 0; i < x; i++) {
    if (i == y) {
      m += (ss[i] == '0');
      continue;
    }
    if (ss[i] == '1') m++;
  }
  cout << m << "\n";
}
