#include "iostream"
#include "climits"
#include "list"
#include "queue"
#include "stack"
#include "set"
#include "functional"
#include "algorithm"
#include "string"
#include "map"
#include "unordered_map"
#include "unordered_set"
#include "iomanip"
#include "cmath"
#include "random"
#include "bitset"
#include "cstdio"
#include "numeric"
#include "cassert"
#include "ctime"

using namespace std;

//constexpr long long int MOD = 1000000007;
constexpr long long int MOD = 998244353;
constexpr double EPS = 1e-8;

//int N, M, K, T, H, W, L, R;
long long int N, M, K, T, H, W, L, R;


int main() {
	ios::sync_with_stdio(false);
	cin.tie(0);

	cin >> N >> M;
	string s;
	cin >> s;
	int w = 0;
	int c = 0;
	int a = 0;
	for (auto i : s) {
		if (i == 'W') {
			w++;
		}
		else if (i == 'C') {
			c++;
			if (c > a) {
				cout << "No" << endl;
				return 0;
			}
		}
		else {
			a++;
			if (a - M > w) {
				cout << "No" << endl;
				return 0;
			}
		}
	}
	cout << "Yes" << endl;
}