#include <cstdio>
#include <cassert>
#include <cstdlib>
#include <cstring>
#include <ctime>
#include <iostream>
#include <algorithm>
#include <vector>
#include <map>
#include <set>
#include <cctype>
#include <utility>
#include <queue>
#include <cmath>
using namespace std;

typedef long long LL;
typedef pair<int, int> PII;
typedef vector<int> VI;
typedef vector<PII> VPII;
typedef pair<LL, LL> PLL;
typedef pair<int, LL> PIL;
typedef pair<LL, int> PLI;
typedef double DB;
typedef long double LD;
#define pb push_back
#define all(x) (x).begin(), (x).end()
#define bit(x) (1 << (x))
#define bitl(x) (1LL << (x))
#define sqr(x) ((x) * (x))
#define sz(x) ((int)(x.size()))
#define counti(x) (__builtin_popcount(x))
#define countl(x) (__builtin_popcountll(x))
#define rep(i, n) for (int (i) = 0; (i) < (int)(n); ++(i))
#define X first
#define Y second

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

template <typename T, typename U>
inline void chkmin(T& x, U y) {
    if (y < x) x = y;
}
int get() {
    char c;
    while (c = getchar(), (c < '0' || c > '9') && (c != '-'));
    bool flag = (c == '-');
    if (flag) c = getchar();
    int x = 0;
    while (c >= '0' && c <= '9') {
        x = x * 10 + c - 48;
        c = getchar();
    }
    return flag ? -x : x;
}

void output(int x) {
    if (x < 0) {
        putchar('-');
        x = -x;
    }
    int len = 0, data[20];
    while (x) {
        data[len++] = x % 10;
        x /= 10;
    }
    if (!len) data[len++] = 0;
    while (len--) putchar(data[len] + 48);
    putchar('\n');
}
int n;
#define MX 1005
VI con[MX];
int size[MX];
int flag;
void DFS(int id, int par) {
    int i;
    size[id] = 1;
    int c = 0, sz = 0;
    for (i = 0; i < con[id].size(); i++) {
        int j = con[id][i];
        if (j == par) continue;
        DFS(j, id);
        size[id] += j;
        if (size[j] > 1) c++;
        sz++;
    }
    if (c >= 2) flag = 1;
    if (c == 1) {
        if (sz > c) flag = 1;
    }
}
int main() {
    
    while (scanf("%d", &n) > 0) {
        int i, u, v;
        flag = 0;
        for (i = 1; i <= n; ++i) con[i].clear();
        for (i = 2; i <= n; i++) {
            
            scanf("%d%d", &u, &v);
            con[u].pb(v);
            con[v].pb(u);
        }
        DFS(1, 0);
        if (flag == 1) puts("NO");
        else puts("YES");
        
    }
    return 0;
}