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: Accepted)

#include<bits/stdc++.h>
using namespace std;
const int N=2e5+5;
typedef pair<int,int>pii;
inline void upa(int&a,const int&b){a<b?a=b:0;}
struct atom{
	int mx,mx2;
	inline void ins(int x){if(x>mx)mx2=mx,mx=x;else if(x>mx2)mx2=x;}
	inline int ask(int x){return x==mx?mx2:mx;}
}f[N];
struct edge{
	int to,next;
}e[N*2];
int n,a,b,md[N*2],sz[N*2],h[N],ecnt=1,i,j,al,mn[N];
char s[N];
long long ans=1;
inline void addedge(int x,int y){
	e[++ecnt]=(edge){y,h[x]};h[x]=ecnt;
	e[++ecnt]=(edge){x,h[y]};h[y]=ecnt;
}
void dfs(int u,int fe){
	sz[fe]=s[u]-'0';
	for(int i=h[u];i;i=e[i].next)if(i^fe^1)
		dfs(e[i].to,i),f[u].ins(md[i]+1),sz[fe]+=sz[i];
	md[fe]=f[u].mx;sz[fe^1]=al-sz[fe];
}
void dfs2(int u,int fe){
	for(int i=h[u];i;i=e[i].next)if(i^fe^1)
		md[i^1]=f[u].ask(md[i]+1),f[e[i].to].ins(md[i^1]+1),dfs2(e[i].to,i);
}
inline void solve(int x){
	static pii a[N];int xb=0,i,j,su=s[x]-'0';
	for(i=h[x];i;i=e[i].next)a[++xb]=pii(md[i]+1,i);
	sort(a+1,a+xb+1);
	for(i=1;i<=xb;){
		for(j=i;j<=xb && a[j].first==a[i].first;++j);
		if(su){if(i<xb)ans+=a[i].first-a[i-1].first;else ans+=2-(a[i].first==a[i-1].first+1);}
		for(;i<j;)su+=sz[a[i++].second];
	}
}
int main(){
	scanf("%d",&n);
	for(i=1;i<n;++i)scanf("%d%d",&a,&b),addedge(a,b);
	scanf("%s",s+1);for(i=1;i<=n;++i)al+=s[i]=='1';
	dfs(1,0);dfs2(1,0);
	for(i=1;i<=n;++i)for(j=h[i],mn[i]=s[i]=='1'?0:N;j;j=e[j].next)
		if(sz[e[j].to])mn[i]=min(mn[i],md[e[j].to]+1);
	for(i=1;i<=n;++i)solve(i);
	printf("%lld\n",ans);
	return 0;
}