#include <cstdio>
#include <cstring>
#include <algorithm>
#include <iostream>
#include <map>
#include <set>
#include <vector>
#include <queue>
#include <stack>
#include <cctype>
#include <climits>
#include <cmath>
using namespace std;
const int maxn = 1005;
int dep[maxn], cnt[maxn];
vector <int> E[maxn];
void dfs(int x, int fa, int d) {
    dep[x] = d;
    for(int i = 0; i < E[x].size(); i++) {
        int u = E[x][i];
        if(u != fa) dfs(u, x, d + 1);
    }
}
int main() {
    int n, x, y;
    while(~scanf("%d", &n)) {
        for(int i = 1; i <= n; i++) {
            E[i].clear();
            cnt[i] = 0;
        }
        for(int i = 1; i < n; i++) {
            scanf("%d%d", &x, &y);
            E[x].push_back(y);
            E[y].push_back(x);
        }
        dfs(1, 0, 1);
        int maxDeep = 0;
        for(int i = 1; i <= n; i++) {
            cnt[dep[i]]++;
            maxDeep = max(maxDeep, dep[i]);
        }
        bool fail = 0;
        for(int i = 1; i <= maxDeep; i++) {
            if(cnt[i] > 1) {
                if(i != maxDeep) fail = 1;
            }
        }
        printf("%s\n", !fail ? "YES" : "NO");
    }
    return 0;
}