#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n >> n;
  string str;
  cin >> str;
  int _count = 1;
  for (int i = 1; i < str.size(); i++) {
    if (str[i] == '#') {
      if (i + 1 - _count < n)
        continue;
      else {
        return printf("NO\n"), 0;
      }
    } else {
      _count = i + 1;
    }
  }
  printf("YES\n");
  return 0;
}
