#pragma GCC optimize ("O3")
#pragma GCC optimize ("unroll-loops")
//#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
#include <bits/stdc++.h>
typedef long long ll;
typedef long double ld;
using namespace std;
const int N = 1e5 + 5;
int n, k;
map<string, int> mp;
int main() {
    ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
    cin >> n >> k;
    cin.ignore();
    for(int i = 0;i < k;i++) {
		string s;
		getline(cin, s);
		int j = 0, cnt = 0;
		while(j < s.size()) {
			if(j + 4 < s.size()) {
				string tmp = s.substr(j, 4);
				if(tmp == "Re: ")
					cnt++, j += 4;
				else {
					break;
				}
			} else {
				break;
			}
		}		
		string tmp = s.substr(j);
		mp[tmp] = max(mp[tmp], cnt + 1);
	}
	int total = 0;
	for(auto i : mp)
		total += i.second;
	if(n >= total)
		cout << "YES";
	else
		cout << "NO";
    return 0;
}