#include <bits/stdc++.h>
using namespace std;
const char EOT = '\n';
const long long INF = (long long)(1e9) * (1024);
const int nmax = (int)(2e3) + 50;
const long long maxn = (long long)(1e5) + 7;
const long long mix = (long long)(1e9) * (-1) - 5;
const long long man = (long long)(1e9) + 5;
const long double pi = 3.1415926535897932384626433832795028841971;
void tipafast() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
}
long long n, x, y, ans = 0;
string s;
int main() {
  cin >> n >> x >> y >> s;
  reverse(s.begin(), s.end());
  for (int i = 0; i < x; i++) {
    if (y == i) {
      if (s[i] == '0') ans++;
    } else {
      if (s[i] == '1') ans++;
    }
  }
  cout << ans;
  return 0;
}
