Problem:
Score : 1900 points

Problem Statement

There is a tree with N vertices.
The vertices are numbered 1 through N.
For each 1 ≤ i ≤ N - 1, the i-th edge connects vertices a_i and b_i.
The lengths of all the edges are 1.

Snuke likes some of the vertices.
The information on his favorite vertices are given to you as a string s of length N.
For each 1 ≤ i ≤ N, s_i is 1 if Snuke likes vertex i, and 0 if he does not like vertex i.

Initially, all the vertices are white.
Snuke will perform the following operation exactly once:

Select a vertex v that he likes, and a non-negative integer d. Then, paint all the vertices black whose distances from v are at most d.

Find the number of the possible combinations of colors of the vertices after the operation.

Constraints

2 ≤ N ≤ 2×10^5

1 ≤ a_i, b_i ≤ N

The given graph is a tree.

|s| = N

s consists of 0 and 1.

s contains at least one occurrence of 1.

Partial Score

In the test set worth 1300 points, s consists only of 1.

Input

The input is given from Standard Input in the following format:

N
a_1 b_1
a_2 b_2
:
a_{N - 1} b_{N - 1}
s

Output

Print the number of the possible combinations of colors of the vertices after the operation.

Sample Input 1

4
1 2
1 3
1 4
1100

Sample Output 1

4

The following four combinations of colors of the vertices are possible:

Sample Input 2

5
1 2
1 3
1 4
4 5
11111

Sample Output 2

11

This case satisfies the additional constraint for the partial score.

Sample Input 3

6
1 2
1 3
1 4
2 5
2 6
100011

Sample Output 3

8

Solution in C++14 (GCC 5.4.1) (judge verdict: Wrong Answer)

#include<bits/stdc++.h>
typedef long long ll;
ll gi(){
	ll x=0,f=1;
	char ch=getchar();
	while(!isdigit(ch))f^=ch=='-',ch=getchar();
	while(isdigit(ch))x=x*10+ch-'0',ch=getchar();
	return f?x:-x;
}
char S[200010];
int fir[200010],dis[400010],nxt[400010],id;
void link(int a,int b){nxt[++id]=fir[a],fir[a]=id,dis[id]=b;}
int F[200010],cF[200010],sz[200010];
void dfs(int x,int fa=-1){
	sz[x]=S[x]-'0';
	for(int i=fir[x];i;i=nxt[i]){
		if(fa==dis[i])continue;
		dfs(dis[i],x);
		if(F[dis[i]]>=F[x])cF[x]=F[x],F[x]=F[dis[i]]+1;
		else cF[x]=std::max(cF[x],F[dis[i]]+1);
		sz[x]+=sz[dis[i]];
	}
}
ll ans;
void DFS(int x,int FF=0,int fa=-1){
	int mx=FF,cm=0;
	for(int i=fir[x];i;i=nxt[i]){
		if(fa==dis[i])continue;
		if(F[dis[i]]+1>mx)cm=mx,mx=F[dis[i]]+1;
		else cm=std::max(cm,F[dis[i]]+1);
	}
	for(int i=fir[x];i;i=nxt[i]){
		if(fa==dis[i])continue;
		int df=FF;
		if(F[x]!=F[dis[i]]+1)df=std::max(df,F[x]);
		else df=std::max(df,cF[x]);
		DFS(dis[i],df+1,x);
	}
	int low=1e9;if(S[x]=='1')low=0;
	for(int i=fir[x];i;i=nxt[i])if(fa!=dis[i]&&sz[dis[i]])low=std::min(low,F[dis[i]]+1);
	if(sz[1]-sz[x])low=std::min(low,FF);
	ans+=std::max(0,std::min(mx,cm+2)-low);
	printf("%d %d %d\n",x,std::min(mx,cm+2)-1,low);
}
int main(){
#ifdef XZZSB
	freopen("in.in","r",stdin);
	freopen("out.out","w",stdout);
#endif
	int n=gi(),u,v;
	for(int i=1;i<n;++i)u=gi(),v=gi(),link(u,v),link(v,u);
	scanf("%s",S+1);
	dfs(1);DFS(1);
	printf("%lld\n",ans+1);
	return 0;
}