#include <iostream>
#include <vector>
#include <cstring>
using namespace std;

int visited[500];
vector<int> G[500];

void dfs(int v) {
    visited[v] = true;
    for (int to : G[v]) {
        if (not visited[to]) dfs(to);
    }
}

int main() {
    int N, M;
    cin >> N >> M;

    vector<int> deg(N, 0);
    memset(visited, -1, sizeof(visited));

    int a, b;
    for (int i = 0; i < M; i++) {
        cin >> a >> b;
        deg[a]++; deg[b]++;
        visited[a] = visited[b] = 0;

        G[a].push_back(b);
        G[b].push_back(a);
    }

    dfs(a);
    for (int i = 0; i < N; i++) {
        if (visited[i] == 0) {
            cout << "NO" << endl;
            return 0;
        }
    }


    int cnt = 0;
    for (int i = 0; i < N; i++) {
        cnt += deg[i] & 1;
    }

    if (cnt <= 2) cout << "YES" << endl;
    else cout << "NO" << endl;

    return 0;
}