#include<bits/stdc++.h>
using namespace std;
const int maxn=2100;
const int INF=0x3f3f3f3f;
int degree[maxn];
int vis[maxn],gra[maxn][maxn];
vector<int>G[maxn];
int n;
bool dfs(int u,int fa,int cn){
    if(cn==n){
        return true;
    }
    for(int i=0;i<G[u].size();i++){
        int v=G[u][i];
        if(vis[v]||v==fa){
            continue;
        }
        vis[v]=1;
        if(dfs(v,u,cn+1))
            return true;
        vis[v]=0;   //如果没有这句，会过不了这个样例。5 2 3 2 4 4 1 1 2 5 4
    }
    return false;
}
void init(){//以后尽量放在前面情况，不装B
    for(int i=0;i<=n+2;i++) 
            G[i].clear();
    memset(degree,0,sizeof(degree));
    memset(vis,0,sizeof(vis));
    memset(gra,0,sizeof(gra));
}
int main(){
    int a,b;
    while(scanf("%d",&n)!=EOF){
        init();
        for(int i=0;i<n;i++){
            scanf("%d%d",&a,&b);
            if(gra[a][b]==1||a==b)
                continue;
            gra[a][b]=gra[b][a]=1;
            G[a].push_back(b);
            G[b].push_back(a);
            degree[a]++,degree[b]++;
        }
        int deg1=0,idx=1;
        for(int i=1;i<=n;i++){
            if(degree[i]==1){
                deg1++;
                idx=i;
            }
        }
        if(deg1>2){ //度为1的大于2个，必然不行
            puts("NO");
            continue;
        }
        vis[idx]=1;
        if(dfs(idx,0,1))
            puts("YES");
        else puts("NO");
    }
    return 0;
}