#include <bits/stdc++.h>
template <typename _Tp>
_Tp gcd(const _Tp &a, const _Tp &b) {
  return (!b) ? a : gcd(b, a % b);
}
template <typename _Tp>
__inline__ __attribute__((always_inline)) _Tp abs(const _Tp &a) {
  return a > 0 ? a : -a;
}
template <typename _Tp>
__inline__ __attribute__((always_inline)) _Tp max(const _Tp &a, const _Tp &b) {
  return a < b ? b : a;
}
template <typename _Tp>
__inline__ __attribute__((always_inline)) _Tp min(const _Tp &a, const _Tp &b) {
  return a < b ? a : b;
}
template <typename _Tp>
__inline__ __attribute__((always_inline)) void chmax(_Tp &a, const _Tp &b) {
  (a < b) && (a = b);
}
template <typename _Tp>
__inline__ __attribute__((always_inline)) void chmin(_Tp &a, const _Tp &b) {
  (a > b) && (a = b);
}
template <typename _Tp>
__inline__ __attribute__((always_inline)) void read(_Tp &x) {
  register char ch(getchar());
  bool f(false);
  while (ch < 48 || ch > 57) f |= ch == 45, ch = getchar();
  x = ch & 15, ch = getchar();
  while (ch >= 48 && ch <= 57)
    x = (((x << 2) + x) << 1) + (ch & 15), ch = getchar();
  if (f) x = -x;
}
template <typename _Tp, typename... Args>
__inline__ __attribute__((always_inline)) void read(_Tp &t, Args &...args) {
  read(t);
  read(args...);
}
__inline__ __attribute__((always_inline)) int read_str(char *s) {
  register char ch(getchar());
  while (ch < 65 || ch > 122 || (ch > 90 && ch < 97)) ch = getchar();
  register char *tar = s;
  *tar = ch, ch = getchar();
  while ((ch >= 65 && ch <= 90) || (ch >= 97 && ch <= 122))
    *(++tar) = ch, ch = getchar();
  return tar - s + 1;
}
const int N = 200005;
char s[N];
int main() {
  int n, x, y;
  read(n, x, y);
  scanf("%s", s + 1);
  int ans = 0;
  for (int i = n - x + 1; i <= n; ++i) {
    if (i != n - y) {
      if (s[i] == '1') {
        ++ans;
      }
    } else {
      if (s[i] == '0') {
        ++ans;
      }
    }
  }
  printf("%d\n", ans);
  return 0;
}
