#include <bits/stdc++.h>
using namespace std;
const int MAXN = 1.5e7 + 10;
const double eps = (double)1e-8;
const double PI = acos(-1.0);
inline bool eq(double a, double b) { return abs(b - a) < eps; }
inline double getdouble() {
  double x;
  scanf("%lf", &x);
  return x;
}
inline int getint() {
  int x;
  scanf("%d", &x);
  return x;
}
inline long long getlonglong() {
  long long x;
  scanf("%lld", &x);
  return x;
}
inline unsigned long long getunsignedlonglong() {
  unsigned long long x;
  scanf("%llu", &x);
  return x;
}
int main() {
  int n = getint(), x = getint(), y = getint();
  string s;
  cin >> s;
  if (y == 0) {
    int p = 0, idx = n - 1;
    if (s[idx] == '0') p++;
    x -= y + 1;
    while (x--) {
      if (s[idx - 1] == '1') p++;
      idx--;
    }
    cout << p << endl;
    return 0;
  }
  int id = n - y - 1, cnt = 0;
  if (s[id] == '0') cnt++;
  x -= y + 1;
  int idd = id;
  while (x--) {
    if (s[idd - 1] == '1') cnt++;
    idd--;
  }
  for (int i = id + 1; i < n; i++) {
    if (s[i] == '1') cnt++;
  }
  cout << cnt << endl;
  return 0;
}
