#include <bits/stdc++.h>
using namespace std;
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
void c_p_c() {}
bool f(long long x, long long y) { return x > y; }
int32_t main() {
  c_p_c();
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  long long n, x, y;
  cin >> n >> x >> y;
  string s;
  cin >> s;
  long long l = s.size();
  long long c = 0;
  for (long long i = n - x; i < n; i++) {
    if (i == n - y - 1)
      c += (s[i] != '1');
    else {
      c += (s[i] != '0');
    }
  }
  cout << c;
}
