#include <iostream>
#include <cstdio>
#include <cstring>

using namespace std;

const int N = 510;

int t, n, m, d[N], fa[N];

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

int main() {
    scanf("%d%d", &n, &m);
    memset(d, 0, sizeof(d));
    for (int i = 1, u, v; i <= m; ++i) {
        scanf("%d%d", &u, &v);
        ++d[u], ++d[v];
        int fu = Find(u), fv = Find(v);
        if (fu != fv) fa[fu] = fv;
    }

    int root = -1, odd = 0;
    for (int i = 0; i < n; ++i) {
        if (!d[i]) continue;
        if (root == -1) root = Find(i);
        else if (Find(i) != root) {
            puts("NO");
            break;
        }
        odd += d[i] & 1;
    }

    puts(odd == 0 || odd == 2 ? "YES" : "NO");

    return 0;
}