#include <bits/stdc++.h>
using namespace std;
void __print(int x) { cerr << x; };
void __print(long x) { cerr << x; };
void __print(long long x) { cerr << x; };
void __print(unsigned x) { cerr << x; };
void __print(unsigned long x) { cerr << x; };
void __print(unsigned long long x) { cerr << x; };
void __print(float x) { cerr << x; };
void __print(double x) { cerr << x; };
void __print(long double x) { cerr << x; };
void __print(char x) { cerr << '\'' << x << '\''; };
void __print(const char *x) { cerr << '\"' << x << '\"'; };
void __print(const string &x) { cerr << '\"' << x << '\"'; };
void __print(bool x) { cerr << (x ? "true" : "false"); }
long long powmod(long long a, long long b) {
  long long res = 1;
  a %= 1000000007;
  assert(b >= 0);
  for (; b; b >>= 1) {
    if (b & 1) res = res * a % 1000000007;
    a = a * a % 1000000007;
  }
  return res;
}
long long string_to_int(string s) {
  long long ans = 0;
  long long p = 1;
  for (long long i = s.size() - 1; i >= 0; i--) {
    ans += (s[i] - '0') * p;
    p *= 10;
  }
  return ans;
}
long long fast_pow(long long a, long long b) {
  if (b == 1) return a;
  if (b == 0) return 1;
  long long x = fast_pow(a, b / 2);
  x *= x;
  if (b & 1) x *= a;
  return x;
}
template <typename T, typename V>
void __print(const pair<T, V> &x) {
  cerr << '{';
  __print(x.first);
  cerr << ',';
  __print(x.second);
  cerr << '}';
}
template <typename T>
void __print(const T &x) {
  long long f = 0;
  cerr << '{';
  for (auto &i : x) cerr << (f++ ? "," : ""), __print(i);
  cerr << "}";
}
void _print() { cerr << "]\n"; }
template <typename T, typename... V>
void _print(T t, V... v) {
  __print(t);
  if (sizeof...(v)) cerr << ", ";
  _print(v...);
}
void t_c_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 ans = 0;
  for (long long i = n - 1; i >= n - x; i--) {
    if (s[i] == '1') {
      ans++;
    }
  }
  if (s[n - y - 1] == '1') {
    ans--;
  }
  if (s[n - y - 1] == '0') {
    ans++;
  }
  cout << ans << '\n';
}
int32_t main() {
  t_c_c();
  return 0;
}
