#include <bits/stdc++.h>

using namespace std;
typedef long long ll;

const int N = 3e5 + 3, MOD = 1e9 + 7;


int main() {

    cin.tie(0);cin.sync_with_stdio(0);
    cout.tie(0);cout.sync_with_stdio(0);

    int n , m ;
    cin >> n >> m;

    int k =0 ;
    map<string , int > mp ;

    while (m--)
    {
        string s ;
        int re = 1 ;

        cin >> s;
        while (s == "Re:")
        {
            cin >> s;
            re++ ;
        }

        mp[s] = max(mp[s] , re);
    }

    for(auto it : mp) k += it.second ;

    cout << (k <= n ? "YES" : "NO");

    return 0;
}