#include <bits/stdc++.h>
using namespace std;
#define int long long
#define ld long double
#define show(x,y) cout << y << " " << #x << endl;
#define show2(x,y,i,j) cout << y << " " << #x << " " << j << " " << #i << endl;
#define show3(x,y,i,j,p,q) cout << y << " " << #x << " " << j << " " << #i << " " << q << " " << #p << endl;
#define show4(x,y) for(auto it:y) cout << it << " "; cout << #x << endl;
typedef pair<int,int>pii;
mt19937_64 rng(chrono::system_clock::now().time_since_epoch().count());
vector<int>adj[1005];
void solve(){
int n,m;
cin >> n >> m;
int temp,temp2;
for(int x=0;x<m;x++){
cin >> temp >> temp2;
adj[temp].push_back(temp2);
adj[temp2].push_back(temp);
}
if(m==n-1)cout << "YES\n";
else cout << "NO\n";
//if(n==1){
//cout << "1\n1\n";
//}
//else if(n==2){
//cout << "2\n1 1\n";
//}
//else if(n>=3){
//cout << (n-2)*2 << "\n";
//for(int y=2;y<n;y++) cout << y << " ";
//for(int y=n-1;y>1;y--) cout << y << " ";
//}
}
int32_t main(){
ios::sync_with_stdio(0);
cin.tie(0);
int t=1;
//cin >> t;
while(t--){
solve();
}
}
