#include <bits/stdc++.h>
using namespace std;
long long spf[31];
long long fac[31];
void sieve() {
  spf[1] = 1;
  for (long long i = 2; i < 31; i++) spf[i] = i;
  for (long long i = 4; i < 31; i += 2) spf[i] = 2;
  for (long long i = 3; i * i < 31; i++) {
    if (spf[i] == i) {
      for (long long j = i * i; j < 31; j += i)
        if (spf[j] == j) spf[j] = i;
    }
  }
}
map<long long, long long> getfactor(long long a) {
  map<long long, long long> m;
  while (a > 1) {
    m[spf[a]]++;
    a /= spf[a];
  }
  return m;
}
long long power(long long x, long long y, long long p) {
  long long res = 1;
  x = x % p;
  if (x == 0) return 0;
  while (y > 0) {
    if (y & 1) res = (res * x) % p;
    y = y >> 1;
    x = (x * x) % p;
  }
  return res;
}
long long gcd(long long a, long long b) {
  if (a == 0) return b;
  return gcd(b % a, a);
}
long long inverse(long long a, long long p) { return power(a, p - 2, p); }
long long ncr(long long n, long long r, long long p) {
  if (r > n) return 0;
  if (r == 0 || r == n) return 1;
  return (fac[n] * inverse(fac[r], p) % p * inverse(fac[n - r], p) % p) % p;
}
bool dp[101][101] = {0};
void solve() {
  long long n, k;
  cin >> n >> k;
  string s;
  cin >> s;
  dp[0][0] = 1;
  long long con = 0, maxi = 0;
  for (long long i = 0; i < n; i++) {
    if (s[i] == 'N') {
      con++;
      maxi = max(con, maxi);
    } else
      con = 0;
  }
  string t;
  t.push_back('Y');
  for (long long i = 0; i < n; i++) t.push_back(s[i]);
  t.push_back('Y');
  if (maxi > k) {
    cout << "NO" << '\n';
    return;
  }
  for (long long i = 1; i <= n; i++) {
    dp[i][0] = 1;
    if (s[i - 1] == 'Y') {
      continue;
    } else {
      for (long long j = 1; j <= n; j++) dp[i][j] = dp[i - 1][j - 1];
    }
  }
  for (long long i = 1; i <= n; i++) {
    if (dp[i][k]) {
      if (t[i - k] != 'N' && t[i + 1] != 'N') {
        cout << "YES" << '\n';
        return;
      }
    }
  }
  cout << "NO" << '\n';
}
signed main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  long long test = 1;
  while (test--) {
    solve();
  }
}
