#include <bits/stdc++.h>
using namespace std;
const int maxn = 1000000;
char road[maxn];
int main() {
  int n, k, i, cnt;
  bool flag;
  while (cin >> n >> k >> road) {
    cnt = 0;
    flag = true;
    for (i = 0; i < n; i++) {
      if (road[i] == '#')
        cnt++;
      else {
        if (cnt >= k) flag = false;
        cnt = 0;
      }
    }
    if (flag)
      cout << "YES\n";
    else
      cout << "NO\n";
  }
  return 0;
}
