#include "bits/stdc++.h"
#define ALL(obj) (obj).begin(),(obj).end()
#define RALL(obj) (obj).rbegin(),(obj).rend()
#define REP(i, n) for(int i = 0; i < (int)(n); i++)
#define REPR(i, n) for(int i = (int)(n); i >= 0; i--)
#define FOR(i,n,m) for(int i = (int)(n); i < int(m); i++)
using namespace std;
typedef long long ll;
const int MOD = 1e9 + 7;
const int INF = MOD - 1;
const ll LLINF = 4e18;

//UnionFind
class UnionFind {
private:
    vector<int> par;
public:
    UnionFind(int n) {
        par.resize(n, -1);
    }

    int root(int x) {
        if (par[x] < 0) return x;
        return par[x] = root(par[x]);
    }

    bool unite(int x, int y) {
        int rx = root(x);
        int ry = root(y);
        if (rx == ry) return false;
        if (size(rx) < size(ry)) swap(rx, ry);
        par[rx] += par[ry];
        par[ry] = rx;
        return true;
    }

    bool same(int x, int y) {
        int rx = root(x);
        int ry = root(y);
        return rx == ry;
    }

    int size(int x) {
        return -par[root(x)];
    }
};

int main() {
    int n, m;
    cin >> n >> m;
    UnionFind uni(n);
    vector<vector<int>> G(n);
    REP(i, m) {
        int a, b;
        cin >> a >> b;
        G[a].push_back(b);
        G[b].push_back(a);
        uni.unite(a, b);
    }
    int r = -INF;
    REP(i, n) {
        if (uni.size(i) > 1) {
            cout << i << endl;
            if (r == -1) {
                r == uni.root(i);
            }
            else if (r != uni.root(i)) {
                puts("NO");
                return 0;
            }
        }
    }
    int cnt = 0;
    REP(i, n) {
        if (G[i].size() % 2 != 0) {
            cnt++;
        }
    }
    if (cnt == 2 || cnt == 0) {
        puts("YES");
    }
    else {
        puts("NO");
    }
    getchar(); getchar();
}