#include <bits/stdc++.h>
using namespace std;
string s;
vector<int> sum;
int n, k, i, kol;
int main() {
  ios_base::sync_with_stdio(0);
  cin >> n >> k;
  cin >> s;
  sum.push_back(0);
  for (i = 1; i < n; i++) {
    if (s[i] == '#') {
      sum.push_back(sum[i - 1] + 1);
    } else
      sum.push_back(sum[i - 1]);
  }
  kol = 0;
  for (i = 1; i < n; i++) {
    if (s[i] == '#') continue;
    if (i > k) {
      kol = sum[i] - sum[i - k - 1];
    }
    if (kol >= k) {
      cout << "NO\n";
      return 0;
    }
  }
  cout << "YES\n";
  return 0;
}
