#include <bits/stdc++.h>
#pragma GCC optimize("O3")
#pragma GCC target("avx2")
using namespace std;
signed main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  long long n, x, y;
  cin >> n >> x >> y;
  string s;
  cin >> s;
  vector<long long> prefs(n);
  vector<bool> ready(n);
  for (long long i = n - 1; i > -1; --i) {
    long long k = n - 1 - i;
    if (k)
      prefs[k] = prefs[k - 1] + (s[i] - '0');
    else
      prefs[k] = s[i] - '0';
    ready[k] = s[i] - '0';
  }
  if (ready[y])
    cout << prefs[x - 1] - 1;
  else
    cout << prefs[x - 1] + 1;
}
