#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <algorithm>
#include <cmath>
#include <map>
#include <set>
#include <vector>
#include <queue>
#include <iostream>
#include <cassert>
#include <bitset>
#include <ctime>

using namespace std;

typedef long long LL;
typedef double DB;
typedef pair<int, int> PII;
typedef vector<int> VI;

#define X first
#define Y second
#define pb push_back

template<class T>
inline void chkmin(T &x, T y) {
    if (y < x) x = y;
}

template<class T>
inline void chkmax(T &x, T y) {
    if (x < y) x = y;
}

const int MN = 1005;
int n;
VI con[MN];

bool dfs(int u, int p) {
    int i, v, cnt(0), j, w;
    
    for (i = con[u].size() - 1; i >= 0; i--) {
        v = con[u][i];
        if (v == p) continue;
        cnt++;    
    }
    if (cnt > 1) {
        for (i = con[u].size() - 1; i >= 0; i--) {
            v = con[u][i];
            if (v == p) continue;
            for (j = con[v].size() - 1; j >= 0; j--) {
                w = con[v][j];
                if (w == u) continue;
                return 0;
            }
        }
        return 1;
    }
    for (i = con[u].size() - 1; i >= 0; i--) {
        v = con[u][i];
        if (v == p) continue;
        return dfs(v, u);
    }
    return 1;
}

int sz, vis[MN], T;

void DFS(int u) {
    int i, v;
    
    sz++;
    vis[u] = T;
    for (i = con[u].size() - 1; i >= 0; i--) {
        v = con[u][i];
        if (vis[v] == T) continue;
        DFS(v);
    }
}

int main() {
    
//    freopen("in.txt", "r", stdin);
//    freopen("out.txt", "w", stdout);
    
    int i, j, k;
    
    while (scanf("%d", &n) == 1) {
        for (i = 0; i < n; i++) con[i].clear();
        for (i = 0; i < n - 1; i++) {
            int j, k;
            scanf("%d%d", &j, &k);
            j--, k--;
            con[j].pb(k);
            con[k].pb(j);
        }
        sz = 0;
        T++;
        DFS(0);
        if (sz != n) {
            puts("NO");
            continue;    
        }
        printf("%s\n", dfs(0, -1) ? "YES" : "NO");
    }
    
    return 0;    
}