#include <bits/stdc++.h>
using namespace std;
long long const oo = 8e18;
double const PI = acos(-1);
int const ooi = 2e9;
int const N = 1e5 + 100;
int const M = 1e6 + 100;
int const MOD = 998244353;
int main() {
  int x, y, n;
  string s;
  cin >> n >> x >> y;
  cin >> s;
  reverse(s.begin(), s.end());
  int cnt = 0;
  for (int i = 0; i < x; ++i) {
    if (i == y) continue;
    if (s[i] == '1') cnt++;
  }
  if (s[y] == '0') cnt++;
  cout << cnt << endl;
  return 0;
}
