#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define int ll
const int N = 5e5 + 7;
int n, m, du[N], f[N], sz[N];
inline int find(int u)
{
    return (f[u] == u ? u : f[u] = find(f[u]));
}
signed main()
{
    ios::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    // freopen("train.in", "r", stdin);
    // freopen("train.out", "w", stdout);
    cin >> n >> m;
    for (int i = 1; i <= n; i++)
        f[i] = i, du[i] = 0, sz[i] = 1;
    for (int i = 1; i <= m; i++)
    {
        int u, v;
        cin >> u >> v;
        u++;
        v++;
        du[u]++;
        du[v]++;
        int fu = find(u), fv = find(v);
        if (fu == fv)
            continue;
        f[fu] = fv;
        sz[fv] += sz[fu];
        sz[fu] = 0;
    }
    int cnt = 0;
    for (int i = 1; i <= n; i++)
        if (du[i] & 1ll)
            cnt++;
    if (cnt != 0 && cnt != 2)
    {
        cout << "NO\n";
        return 0;
    }
    int siz = 0, mx = 0;
    for (int i = 1; i <= n; i++)
    {
        if (sz[find(i)] == 1)
            siz++;
        else
            mx = sz[find(i)];
    }
    if (mx == n - siz)
        cout << "YES\n";
    else
        cout << "NO\n";
}