#include <iostream>
#include <vector>
#include <algorithm>
#include <cmath>
#include <queue>
#include <string>
#include <map>
#include <set>
#include <stack>
#include <tuple>
#include <deque>
#include <array>
#include <numeric>
#include <bitset>
#include <iomanip>
#include <cassert>
#include <chrono>
#include <random>
#include <limits>
#include <iterator>
#include <functional>
#include <sstream>
#include <fstream>
#include <complex>
#include <cstring>
#include <unordered_map>
using namespace std;

using ll = long long;
using P = pair<int, int>;
constexpr int INF = 1001001001;
constexpr int mod = 1000000007;
// constexpr int mod = 998244353;

template<class T>
inline bool chmax(T& x, T y){
    if(x < y){
        x = y;
        return true;
    }
    return false;
}
template<class T>
inline bool chmin(T& x, T y){
    if(x > y){
        x = y;
        return true;
    }
    return false;
}

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

    int N, M;
    cin >> N >> M;
    vector<vector<int>> graph(N);
    for(int i = 0; i < M; ++i){
        int u, v;
        cin >> u >> v;
        graph[u].emplace_back(v);
        graph[v].emplace_back(u);
    }

    int s = 0;
    for(int i = 0; i < N; ++i){
        if(graph[i].size()){
            s = i;
            break;
        }
    }
    queue<int> que;
    que.emplace(s);
    vector<bool> used(N);
    used[s] = true;
    int edge_cnt = 0;
    while(!que.empty()){
        int from = que.front();
        que.pop();
        for(int to : graph[from]){
            if(!used[to]){
                used[to] = true;
                edge_cnt += 1;
                que.emplace(to);
            }
        }
    }
    cout << edge_cnt << endl;
    if(edge_cnt != M){
        cout << "NO\n";
        return 0;
    }

    int cnt = 0;
    for(int i = 0; i < N; ++i)  cnt += graph[i].size() % 2;
    if(cnt == 2)   cout << "YES\n";
    else    cout << "NO\n";

    return 0;
}