#include <iostream>
#include <set>
using namespace std;
int main() {
int n,m;
cin>>n>>m;
int ms[n][n]={};
set<int> g[n];
for(int i=0; i<m; i++){
int a,b;
cin>>a>>b;
a--; b--;
g[a].insert(b);
g[b].insert(a);
}
int x=n-1;
string s="YES\n";
for(int i=0; i<n; i++){
if(g[i].size()!=x) s="NO\n";
}
cout<<s;
return 0;
}
I2luY2x1ZGUgPGlvc3RyZWFtPgojaW5jbHVkZSA8c2V0Pgp1c2luZyBuYW1lc3BhY2Ugc3RkOwoKaW50IG1haW4oKSB7CglpbnQgbixtOwoJY2luPj5uPj5tOwoJaW50IG1zW25dW25dPXt9OwoJc2V0PGludD4gZ1tuXTsKCWZvcihpbnQgaT0wOyBpPG07IGkrKyl7CgkJaW50IGEsYjsKCQljaW4+PmE+PmI7CgkJYS0tOyBiLS07CgkJZ1thXS5pbnNlcnQoYik7CgkJZ1tiXS5pbnNlcnQoYSk7CgkJCgl9CglpbnQgeD1uLTE7CglzdHJpbmcgcz0iWUVTXG4iOwoJZm9yKGludCBpPTA7IGk8bjsgaSsrKXsKCQlpZihnW2ldLnNpemUoKSE9eCkgcz0iTk9cbiI7Cgl9Cgljb3V0PDxzOwoJcmV0dXJuIDA7Cn0=
NSAxMAoxIDIKMSAzCjEgNQoyIDMKMiA1CjMgMgo0IDEKNCAzCjQgNQo1IDM=
5 10 1 2 1 3 1 5 2 3 2 5 3 2 4 1 4 3 4 5 5 3
language:
C++ (gcc 8.3)
created:
14 days ago
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