#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=1000+100;
vector<int>G[maxn];
int vis[maxn];
int height[maxn],height1[maxn];
int vis1[maxn];
int siz[maxn];

void init(int n){
    for(int i=1;i<=n;i++){
        G[i].clear();
        siz[i]=1;
    }
    mem0(vis);
    mem0(vis1);
    mem0(height1);
}

void dfs(int u){
    vis[u]=1;
    for(int i=0;i<G[u].size();i++){
        int v=G[u][i];
        if(vis[v]==1)
            continue;
        height[v]=height[u]+1;
        dfs(v);
        siz[u]+=siz[v];
    }
}

int main(){
    int n;
    int u,v;
    while(scanf("%d",&n)!=EOF){
        init(n);
        for(int i=1;i<n;i++){
            scanf("%d%d",&u,&v);
            G[u].push_back(v);
            G[v].push_back(u);
        }
        height[1]=1;
        dfs(1);
        int flag=1;
        for(int i=1;i<=n;i++){
            height1[height[i]]++;
            if(siz[i]>=2)
                vis1[height[i]]=1;
            if(height1[height[i]]>=2&&vis1[height[i]]==1){
                flag=0;
                break;
            }
        }
        if(flag==1){
            printf("YES\n");
        }
        else
            printf("NO\n");
    }
    return 0;
}