#include <bits/stdc++.h>
using namespace std;

using int64 = long long;
using uint64 = unsigned long long;

const int MAX_N = 510;

int deg[MAX_N];
bool isVisited[MAX_N];
vector<int> G[MAX_N];

void dfs(int v)
{
    isVisited[v] = true;

    for (int to : G[v])
    {
        if (!isVisited[to])
        {
            dfs(to);
        }
    }
}

int main()
{
    cin.tie(nullptr);
    ios::sync_with_stdio(false);

    int N, M;
    cin >> N >> M;

    int start = -1;
    vector<int> deg(N, 0);
    for (int i = 0; i < M; i++)
    {
        int a, b;
        cin >> a >> b;

        G[a].push_back(b); deg[a]++;
        G[b].push_back(a); deg[b]++;

        start = a;
    }

    dfs(start);

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

        if (oddCnt > 2 or (!isVisited[i] and (deg[i] > 0)))
        {
            cout << "NO" << endl;
            return 0;
        }
    }

    cout << "YES" << endl;

    return 0;
}