#include <cstring>
#include <cmath>
#include <cstdio>
#include <climits>
#include <ctime>
#include <cassert>
#include <cctype>
#include <iostream>
#include <algorithm>
#include <numeric>
#include <map>
#include <set>
#include <queue>
#include <string>
#include <vector>
#include <bitset>
#include <utility>

#define all(x) (x).begin(), (x).end()
#define bit(x) (1 << (x))
#define cnt1(x) (__builtin_popcount(x))
#define LB lower_bound
#define LET(it,v) __typeof(v) it(v)
#define mset0(x) memset((x), 0, sizeof((x)))
#define mset1(x) memset((x), -1, sizeof((x)))
#define pb push_back
#define PQ priority_queue
#define REP(it,v) for(LET(it,v.begin());it!=v.end();it++)
#define sqr(x) ((x)*(x))
#define sz(x) ((int)(x.size()))
#define UB upper_bound
#define X first
#define Y second

using namespace std;
typedef long long LL;
typedef double DB;
typedef pair<int, int> pii;
typedef pair<LL, LL> pll;
typedef vector<int> vi;
typedef vector<pii> vpii;

template <class T> inline void chkmin(T &a, T b) {
    if (b < a) a = b;
}
template <class T> inline void chkmax(T &a, T b) {
    if (a < b) a = b;
}

const int MX = 1005;
vi con[MX];
int cnt[MX], dp[MX];

void DFS(int u, int pr) {
    dp[u] = dp[pr] + 1;
    cnt[dp[u]]++;
    for (int i = 0; i < sz(con[u]); i++) {
        int v = con[u][i];
        if (v == pr) continue;
        DFS(v, u);
    }
}

int main() {
    
    int n, i, j, u, v;
    while (scanf("%d", &n) == 1) {
        for (i = 1; i <= n; i++) {
            con[i].clear();
            cnt[i] = 0;
        }
        
        for (i = 1; i < n; i++) {
            scanf("%d%d", &u, &v);
            con[u].pb(v);
            con[v].pb(u);
        }
        DFS(1, 0);
        
        for (i = n; i > 1; i--) if (cnt[i] > 1) {
            for (j = i + 1; j <= n; j++) if (cnt[j]) break;
            if (j <= n) break;
        }
        if (i > 1) puts("NO");
        else puts("YES");
    }
    
    return 0;
}