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 <cstdio>
#include <iostream>
#define travel(x, y, i) for (int i = fir[x], y = e[i].to; i; i = e[i].nxt, y = e[i].to)
using namespace std;

const int N = 2e5 + 50;

struct edge {
  int nxt, to;
} e[N << 1];
int fir[N], cnt = 0;
int n, Max[N], low[N], high[N];
char s[N];

inline void addedge(int x, int y) {
  e[++ cnt] = (edge) { fir[x], y }; fir[x] = cnt;
}

inline void Dfs(int x, int fa) {
  travel(x, y, i)
    if (y != fa) {
      Dfs(y, x);
      Max[x] = max(Max[x], Max[y] + 1);
    }
}

inline void Dfslow(int x, int fa, int lo) {
  
}

inline void Dfshigh(int x, int fa, int lo) {
  int mx = ++ lo, sb = 0;
  travel(x, y, i)
    if (y != fa) {
      if (mx < Max[y] + 1) {
        sb = mx; mx = Max[y] + 1;
      }
      else sb = max(sb, Max[y] + 1);
    }
  high[x] = min(mx - 1, sb + 1);
  travel(x, y, i)
    if (y != fa) Dfshigh(y, x, max(lo, Max[y] + 1 != mx ? mx : sb));
}

int main() {
  scanf("%d", &n);
  for (int i = 1, x, y; i < n; i ++) {
    scanf("%d%d", &x, &y);
    addedge(x, y); addedge(y, x);
  }
  scanf("%s", s + 1);
  Dfs(1, 0);
  Dfshigh(1, 0, -1);
  long long ans = 1;
  // for (int i = 1; i <= n; i ++) cerr << Max[i] << " ";cerr << endl;
  // for (int i = 1; i <= n; i ++) cerr << high[i] << " ";cerr << endl;
  for (int i = 1; i <= n; i ++) ans += high[i] - low[i] + 1;
  printf("%lld\n", ans);
  return 0;
}