#include <bits/stdc++.h>
using namespace std;
int conversion(string p) {
  int o;
  o = atoi(p.c_str());
  return o;
}
string toString(int h) {
  stringstream ss;
  ss << h;
  return ss.str();
}
string toStringLong(long long h) {
  stringstream ss;
  ss << h;
  return ss.str();
}
long long gcd(long long a, long long b) { return (b == 0 ? a : gcd(b, a % b)); }
int lcm(int a, int b) { return (a * (b / gcd(a, b))); }
int main() {
  int n, k;
  cin >> n >> k;
  string x;
  cin >> x;
  int i = 0;
  while (i < n) {
    int var = i;
    int suma = i + k;
    if (suma >= n) {
      cout << "YES" << endl;
      return 0;
    } else {
      i = suma;
      while (x[i] == '#') {
        i--;
        if (i == var) {
          cout << "NO" << endl;
          return 0;
        }
      }
    }
  }
}
