#include <bits/stdc++.h>
using namespace std;
int main() {
  long long n, a, b;
  cin >> n >> a >> b;
  long long ma, mi;
  ma = max(a, b);
  mi = min(a, b);
  long long seated = 0;
  for (long long i = (long long)(0); i < (long long)(n); i++) {
    char t;
    cin >> t;
    while (t == '.' and i < n) {
      if (ma != 0) {
        ma--;
        seated++;
      }
      a = ma;
      ma = mi;
      mi = a;
      i++;
      if (i < n) cin >> t;
    }
    a = ma;
    ma = max(mi, ma);
    mi = min(mi, a);
  }
  cout << seated << endl;
  return 0;
}
