#include <bits/stdc++.h>
using namespace std;
inline int read() {
  int neg = 1, num = 0;
  char c = getchar();
  for (; !isdigit(c); c = getchar())
    if (c == '-') neg = -1;
  for (; isdigit(c); c = getchar()) num = (num << 1) + (num << 3) + c - '0';
  return neg * num;
}
int n, a, b;
char s[300010];
int main() {
  n = read();
  a = read();
  b = read();
  scanf("%s", s + 1);
  int las = 0, sum = 0;
  s[n + 1] = '*';
  for (int i = 1; i <= n + 1; i++)
    if (s[i] == '*') {
      int x = (i - las - 1) / 2, y = i - las - 1 - x;
      if (a > b) swap(a, b);
      sum += min(a, x) + min(b, y);
      a = max(0, a - x);
      b = max(0, b - y);
      las = i;
    }
  printf("%d", sum);
  return 0;
}
