#include <iostream>
#include <algorithm>
#include <cstring>
#include <cstdio>
#include <set>

using namespace std;

const int N = 510;

int t, n, m, d[N], fa[N];
set<int> p, s;

bool Check() {
    int cnt = 0;
    for (auto e : p) {
        if (d[e] % 2 != 0) {
            ++cnt;
        }
    }
    if (cnt == 0 || cnt == 2) return true;
    else return false;
}

int Find(int x) { return fa[x] ? fa[x] = Find(fa[x]) : x; }

int main() {
    // freopen("train.in", "r", stdin);
    // freopen("train.out", "w", stdout);

    scanf("%d%d", &n, &m);
    memset(d, 0, sizeof(d));
    memset(fa, 0, sizeof(fa));
    p.clear();
    s.clear();
    for (int i = 1, u, v; i <= m; ++i) {
        scanf("%d%d", &u, &v);
        int fx = Find(u), fy = Find(v);
        if (fx != fy) {
            fa[fx] = fy;
        }
        ++d[u], ++d[v];
        p.insert(u);
        p.insert(v);
    }

    for (auto e : p) s.insert(Find(e));
    if (s.size() >= 2) {
        puts("NO");
        return 0;
    }

    if (!Check()) {
        puts("NO");
    } else {
        puts("YES");
    }

    return 0;
}