#pragma comment(linker, "/STACK:1024000000,1024000000")
#include <map>
#include <set>
#include <stack>
#include <queue>
#include <cmath>
#include <ctime>
#include <vector>
#include <cstdio>
#include <cctype>
#include <cstring>
#include <cstdlib>
#include <iostream>
#include <algorithm>
using namespace std;
#define INF 0x3f3f3f3f
#define inf -0x3f3f3f3f
#define lson l,m,rt<<1
#define rson m+1,r,rt<<1|1
#define mem0(a) memset(a,0,sizeof(a))
#define mem1(a) memset(a,-1,sizeof(a))
#define mem(a, b) memset(a, b, sizeof(a))
typedef long long ll;
const int maxn=1010;
int mp[maxn][maxn];
int f[maxn];
int degree[maxn];
int p,root,n;

void dfs(int x,int c)
{
    int i,j,k;
    if(c==n)
        p=1;
    if(p)
        return;
    for(i=0;i<n;i++)
        if(mp[x][i]==1&&f[i]==1){
            f[i]=0;
            dfs(i,c+1);
            f[i]=1;
        }
}

void HamiltonianGraph(){
    int i;
    for(i=0;i<n;i++)
        f[i]=1;
    f[root]=0;
    dfs(root,1);
    if(p)
        puts("YES");
    else
        puts("NO");
}

int main(){
    int x,y;
    while(scanf("%d",&n)!=EOF){
        mem0(mp);
        mem0(degree);
        for(int i=1;i<=n;i++){
            scanf("%d%d",&x,&y);
            x--;
            y--;
            mp[x][y]=mp[y][x]=1;
            degree[x]++;
            degree[y]++;
        }
        int cnt=0;
        int flag=1;
        root=0;
        for(int i=0;i<n;i++){
            if(degree[i]==0){
                flag=0;
                break;
            }
            else if(degree[i]==1){
                cnt++;
                root=i;
            }
        }
        if(flag==0||cnt>=3){
            printf("NO\n");
            continue;
        }
        if(cnt==0&&flag==1){
            printf("YES\n");
            continue;
        }
        p=0;
        HamiltonianGraph();
    }
}