/// Msaa el 5ra
#pragma GCC optimize("O3")
#pragma GCC optimize ("unroll-loops")
#pragma GCC target("avx,avx2,fma")

#include "bits/stdc++.h"

using namespace std;

#define pb push_back
#define F first
#define S second
#define f(i, a, b)  for(int i = a; i < b; i++)
#define all(a)  a.begin(),a.end()
#define rall(a) a.rbegin(),a.rend()
#define sz(x) (int)(x).size()
#define mp(x, y) make_pair(x,y)
#define popCnt(x) (__builtin_popcountll(x))
#define int ll

using ll = long long;
using ii = pair<int, int>;
using ull = unsigned long long;

const int N = 5e5 + 5, LG = 18, MOD = 1e9 + 7;
const long double PI = acos(-1);
const long double EPS = 1e-7;

void doWork() {

    int n, k;
    cin >> n >> k;
    cin.ignore();
    vector<string> vec;
    f(i, 0, k) {
        string s;
        getline(cin, s);
        vec.push_back(s);
    }
    sort(all(vec), [&](string a, string b) {
        return a.size() < b.size();
    });
    set<string> st;
    int cnt = 0;
    f(i, 0, k) {
        cnt += 1;
        for (int j = 0; j < vec[i].size(); j++) {
            if (j + 4 <= vec[i].size() && vec[i].substr(j, 4) == "Re: ") {
                cnt += 1;
            }
            if (j > 4 && vec[i].substr(j - 4, 4) == "Re: " && st.count(vec[i].substr(j))) {
                cnt -= 1;
            }
        }
        st.insert(vec[i]);
    }
    if (cnt <= n)
        cout << "YES\n";
    else
        cout << "NO\n";


}

int32_t main() {
#ifdef ONLINE_JUDGE
    ios_base::sync_with_stdio(0);
    cin.tie(0);
#endif // ONLINE_JUDGE

    int t = 1;
//    cin >> t;
    while (t--) {
        doWork();
    }
}