#include <bits/stdc++.h>
using namespace std;
int n, m, k;
char a[500006];
int main() {
  while (scanf("%d%d", &n, &m) != EOF) {
    scanf("%s", a);
    int len = strlen(a), flag = 0, biao = 0, i;
    for (i = 1; i < len; i++) {
      if (a[i] == '.') {
        if ((i - biao) > m) {
          flag = 1;
          break;
        } else {
          biao = i;
        }
      }
    }
    if (flag == 0 && i == len)
      printf("YES\n");
    else
      printf("NO\n");
  }
}
