#include<bits/stdc++.h>
using namespace std;
vector<int> haha[10000];
vector<int> wow(0);
vector<int> wut(0);
int n,m;
void dfs(int a, int t, int d) {
if(d%2) {
wow.push_back(a);
}
else {
wut.push_back(a);
}
for(int v: haha[a]) {
if(v != t) {
dfs(v,a,d+1);
}
}
}
bool check() {
vector<int> br(n+1);
vector<int> br1(n+1);
for(int i = 1; i <= n; i++) {
br[i] = haha[i].size();
}
for(int a: wow) {
if(haha[a].size() == 1) {
br[haha[a][0]]--;
br[a] = -1;
}
}
for(int i = 1; i <= n; i++) {
br1[i] = br[i];
}
for(int i = 1; i <= n; i++) {
if(br1[i] == 1) {
for(int v: haha[i]) {
br[v]--;
}
br[i] = -1;
}
}
for(int i = 1; i <= n; i++) {
if(br[i] > 2) {
return false;
}
}
return true;
}
int main()
{
ios_base::sync_with_stdio(false);
cin.tie(NULL);
cout.tie(NULL);
cin >> n >> m;
int a,b;
for(int i = 0; i < m; i++) {
cin >> a >> b;
haha[a].push_back(b);
haha[b].push_back(a);
}
if(m > n-1) {
cout << "NO" << endl;
return 0;
}
dfs(1,-1,0);
if(check()) {
cout << "YES" << endl;
}
else {
swap(wow,wut);
if(check()) {
cout << "YES" << endl;
}
else {
cout << "NO" << endl;
}
}
return 0;
}
