#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"); }
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) {
  int 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...);
}
const int mod = 1e9 + 7, num = 1e5 + 1;
inline long long int add(long long int x, long long int y) {
  x += y;
  if (x >= mod) x -= mod;
  return x;
}
inline long long int sub(long long int x, long long int y) {
  x -= y;
  if (x < 0) x += mod;
  return x;
}
inline long long int mul(long long int x, long long int y) {
  return (x * 1ll * y) % mod;
}
bool comp(string s1, string s2) { return s1.size() < s2.size(); }
void solve(int io) {
  long long int n, x, y;
  cin >> n >> x >> y;
  string s;
  cin >> s;
  long long int cnt = 0, ans = 0;
  y = n - y - 1;
  x = n - x;
  for (long long int i = n - 1; i >= x; i--) {
    if (s[i] == '1' && i != y) {
      ans++;
    }
    if (i == y && s[i] == '0') {
      ans++;
    }
  }
  cout << ans << "\n";
}
int main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  using namespace std::chrono;
  auto startTime = high_resolution_clock::now();
  long long int test = 1;
  for (long long int i = 0; i < test; i++) {
    solve(i + 1);
  }
  auto endTime = high_resolution_clock::now();
  auto duration = duration_cast<seconds>(endTime - startTime);
}
