#include <bits/stdc++.h>
using namespace std;
int main () {
    int N, M;
    cin >> N >> M;
    string s;
    cin >> s;
    int cc = 0;
    std::vector<int> V1, V2;
    for (int i = 0; i < (N + M) * 2; i ++) {
        if (s[i] == 'W') {
            V1.push_back(1);
        } else if (s[i] == 'C') {
            V2.push_back(-1);
        } else if (cc < M) {
            V2.push_back(1);
            cc ++;
        } else {
            V1.push_back(-1);
        }
    }
    int a = 0;
    for (auto x : V1) {
        a += x;
        if (a < 0) {
            cout << "No" << endl;
            return 0;
        }
    }
    for (auto x : V2) {
        a += x;
        if (a < 0) {
            cout << "No" << endl;
            return 0;
        }
    }
    cout << "Yes" << endl;
}