Each New Year Timofey and his friends cut down a tree of n vertices and bring it home. After that they paint all the n its vertices, so that the i-th vertex gets color ci.

Now it's time for Timofey birthday, and his mother asked him to remove the tree. Timofey removes the tree in the following way: he takes some vertex in hands, while all the other vertices move down so that the tree becomes rooted at the chosen vertex. After that Timofey brings the tree to a trash can.

Timofey doesn't like it when many colors are mixing together. A subtree annoys him if there are vertices of different color in it. Timofey wants to find a vertex which he should take in hands so that there are no subtrees that annoy him. He doesn't consider the whole tree as a subtree since he can't see the color of the root vertex.

A subtree of some vertex is a subgraph containing that vertex and all its descendants.

Your task is to determine if there is a vertex, taking which in hands Timofey wouldn't be annoyed.

The first line contains single integer n (2?≤?n?≤?105) — the number of vertices in the tree.

Each of the next n?-?1 lines contains two integers u and v (1?≤?u,?v?≤?n, u?≠?v), denoting there is an edge between vertices uand v. It is guaranteed that the given graph is a tree.

The next line contains n integers c1,?c2,?...,?cn (1?≤?ci?≤?105), denoting the colors of the vertices.

PRint "NO" in a single line, if Timofey can't take the tree in such a way that it doesn't annoy him.

Otherwise print "YES" in the first line. In the second line print the index of the vertex which Timofey should take in hands. If there are multiple answers, print any of them.

41 22 33 41 2 1 1output
YES2input
31 22 31 2 3output
YES2input
41 22 33 41 2 1 2output
NO題意: 一棵樹中各個節(jié)點被染上了c[i]顏色; 讓你在一棵樹中隨便選一個節(jié)點作為根節(jié)點,然后把整棵樹抬起來; 問你是否存在一個根節(jié)點，這個根節(jié)點的直系兒子節(jié)點的子樹里面的所有節(jié)點的顏色都一樣; 
思路：
要理解樹的構造以及特點，每棵樹的子樹是不相連的，就是幾個分塊了，所以這個點要想使所有子樹都是一種顏色，其實就是這個點所連邊包括所有端點不同色的邊，因為還有端點不同色的邊沒有與根節(jié)點相連，那么肯定某一顆子樹含有這個邊，也就是這顆子樹并沒有同色，因為子樹之間沒有邊相連，所以只能在某一科子樹里。所以做法就是記錄所有不同色的邊的個數(shù)，記錄每個點連接的不同色的邊的個數(shù)，如果某個兩者相等說明這個點連著所有不同色的邊，也就是符合題意了
#include <iostream>#include <cstdio>#include <algorithm>using namespace std;const int maxn = 2e5 + 5;int u[maxn], v[maxn], cnt[maxn], c[maxn], sum = 0;int main(){    int n;    cin >> n;    for(int i = 1; i < n; i++)        cin >> u[i] >> v[i];    for(int i = 1; i <= n; i++)        cin >> c[i];    for(int i = 1; i < n; i++)    {        if(c[u[i]] != c[v[i]])            sum++, cnt[u[i]]++, cnt[v[i]]++;    }    for(int i = 1; i <= n; i++)    {        if(cnt[i] == sum)        {            cout << "YES/n" << i << endl;            return 0;        }    }    cout << "NO" << endl;    return 0;}