#include<cstdio>
#include<iostream>
#include<algorithm>
#include<cstring>
using namespace std;
typedef long long ll;
const int maxn = 200005, inf = 0x3f3f3f3f;

inline int read()
{
	int ret, f=1;
	char c;
	while((c=getchar())&&(c<'0'||c>'9'))if(c=='-')f=-1;
	ret=c-'0';
	while((c=getchar())&&(c>='0'&&c<='9'))ret=(ret<<3)+(ret<<1)+c-'0';
	return ret*f;
}

int n;
char s[maxn];
ll ans;

int head[maxn], tot;
struct edge{
	int nxt, to;
}e[maxn<<1];

void Addedge(int x, int y)
{
	e[++tot] = (edge){head[x], y};
	head[x] = tot;
}

int f[maxn][2], siz[maxn], bat[maxn];

void dfs1(int x, int fa)
{
	siz[x] = (s[x] == '1');
	bat[x] = (s[x] == '1'? 0: inf);
	int id;
	for(int i = head[x]; i; i = e[i].nxt)
	{
		id = e[i].to;
		if(id == fa)	continue;
		dfs1(id, x);
		if(f[id][0] + 1 > f[x][0])
		{
			f[x][1] = f[x][0];
			f[x][0] = f[id][0] + 1;
		}
		else if(f[id][0] + 1 > f[x][1])
		{
			f[x][1] = f[id][0] + 1;
		}
		siz[x] += siz[id];
		if(siz[id])
			bat[x] = min(bat[x], f[id][0] + 1);
	}
}

void dfs2(int x, int fa)
{
	ans += max(min(f[x][0], f[x][1] + 2) - bat[x], 0);
	int id, tmp;
	for(int i = head[x]; i; i = e[i].nxt)
	{
		id = e[i].to;
		if(id == fa)	continue;
		tmp = (f[x][0] == f[id][0] + 1? f[x][1]: f[x][0]) + 1;
		if(tmp + 1 > f[id][0])
		{
			f[id][1] = f[id][0];
			f[id][0] = tmp;
		}
		else if(tmp + 1 > f[id][1])
			f[id][1] = tmp;
		if(siz[id] != siz[1])	bat[id] = min(bat[id], tmp);
		dfs2(id, x);
	}
}

int main()
{
	n = read();
	int u, v;
	for(int i = 1; i < n; ++i)
	{
		u = read();
		v = read();
		Addedge(u, v);
		Addedge(v, u);
	}
	scanf("%s", s + 1);
	dfs1(1, 0);
	dfs2(1, 0);
	printf("%lld", ans + 1);
	return 0;
}