#include<bits/stdc++.h> 

using namespace std;

int main()
{
    map<int, int>mp;
    int n, m;
    cin >> n >> m;
 for (int i = 1;i < n+1;i++) {
        mp.insert(pair<int, int>(i, 0));
    }
 for (map<int, int>::iterator it = mp.begin();it != mp.end();it++) {
     //cout << it->first << " " << it->second << endl;
 }
    int a[10][2];
    for (int i = 0;i < m;i++) {
        for (int j = 0;j < 2;j++) {
            cin >> a[i][j];
            
        }
            int key1 = a[i][0];
            int key2 = a[i][1];
            map<int, int>::iterator it1 = mp.find(key1);
            it1->second++;
            map<int, int>::iterator it2 = mp.find(key2);
            it2->second--;
    }
    int count1 = 0;
    int count2 = 0;
    for (map<int, int>::iterator it = mp.begin();it != mp.find(n+1);it++) {
        //cout << it->first << " " << it->second<<endl;
        if (it->second <= -1)count1++;
        if (it->second >= 1)count2++;
    }
    //cout << count1 << count2 << endl;
    if ((count1 == 1) && (count2 == 1)) {
        cout << "Yes";
    }
    else {
        cout << "No";
    }

    return 0;
}