#include<cstdio>
#include<cstring>
#include<vector>

using namespace std;

const int maxn = 1010;
vector<int> G[maxn];
int d[maxn];

void dfs(int u,int fa,int dis)
{
    d[u] = dis;
    for(int i=0;i<G[u].size();++i)
    {
        if(G[u][i] == fa) continue;
        dfs(G[u][i],u,dis+1);
    }
}

int main()
{
    //freopen("test.txt","r",stdin);
    int n;
    while(scanf("%d",&n)==1)
    {
        for(int i=0;i<maxn;++i) G[i].clear();
        for(int i=1;i<n;++i)
        {
            int u,v;
            scanf("%d %d",&u,&v);
            G[u].push_back(v);
            G[v].push_back(u);
        }
        dfs(1,-1,0);
        bool flag = true;
        for(int i=2;i<=n;++i)
        {
            for(int j=i+1;j<=n;++j)
            {
                if(d[i] == d[j] && (G[i].size()>1 || G[j].size()>1))
                {
                       flag = false;
                    break;
                }
            }
            if(!flag) break;
        }
        puts(flag?"YES":"NO");
    }
    return 0;
}