#include <bits/stdc++.h>
using namespace std;
const double PI = acos(-1.0);
const long long INF = 1e9 + 47;
const long long LINF = INF * INF;
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
int main() {
  ios_base::sync_with_stdio(0), cin.tie(0), cout.tie(0);
  int n, x, y;
  cin >> n >> x >> y;
  string s;
  cin >> s;
  int ans = 0;
  reverse(s.begin(), s.end());
  s.resize(x);
  for (int i = (0); i < (x); ++i) {
    if (i == y)
      ans += s[i] == '0';
    else
      ans += s[i] == '1';
  }
  cout << ans << endl;
  cerr << "Time elapsed: " << clock() / (double)CLOCKS_PER_SEC << endl;
  return 0;
}
