#include <bits/stdc++.h>
using namespace std;
int main() {
  int sectors;
  int jump_len;
  char sec_info;
  scanf("%d %d", &sectors, &jump_len);
  int num_cont_rocks = 0;
  int i = 0;
  getchar();
  int max_rocks = 0;
  int prev_rock = 0;
  for (int i = 0; i < sectors; i++) {
    scanf("%c", &sec_info);
    if (sec_info == '.') prev_rock = 0;
    if (prev_rock == 0 && sec_info == '#') {
      num_cont_rocks = 1;
      prev_rock = 1;
    } else if (prev_rock == 1 && sec_info == '#') {
      num_cont_rocks++;
    }
    if (num_cont_rocks > max_rocks) max_rocks = num_cont_rocks;
  }
  if (max_rocks >= jump_len)
    cout << "NO" << endl;
  else
    cout << "YES" << endl;
  return 0;
}
