#include <stdio.h>
#include <iostream>
#include <algorithm>
#include <memory.h>

using namespace std;
typedef long long LL;
const int maxn = 400005;

int ehead[maxn],ecnt;
struct edge {
	int u,v,next;
}edg[maxn<<1];
void add(int u,int v) {
	edg[++ecnt]=(edge){u,v,ehead[u]};
	ehead[u]=ecnt;
	edg[++ecnt]=(edge){v,u,ehead[v]};
	ehead[v]=ecnt;
}
char s[maxn];int n,low[maxn],high[maxn];LL ans;
int fa[maxn],f[maxn],g[maxn],stk[maxn],top,pos[maxn],idx;
int pre[maxn],suf[maxn],lowf[maxn],d[maxn];

void upd(int &x,int y) {x<y?x=y:0;}
void dnd(int &x,int y) {x>y?x=y:0;}
void dfs(int u) {
	low[u]=lowf[u]=1<<29;pos[++idx]=u;
	if (s[u]=='1') low[u]=lowf[u]=0;
	for (int v,j=ehead[u];j;j=edg[j].next)
	if ((v=edg[j].v)!=fa[u]) {
		fa[v]=u;dfs(v);f[u]=max(f[u],f[v]+1);
		low[u]=min(low[u],max(low[v]-1,f[v]+1));
	}
}
void solve(int u) {
	int mx1=0,mx2=0,cur;top=0;
	g[u]>mx1?(mx2=mx1,mx1=g[u]):(g[u]>mx2?mx2=g[u]:0);
	for (int v,j=ehead[u];j;j=edg[j].next)
		if ((v=edg[j].v)!=fa[u]) stk[++top]=v;
	
	pre[0]=suf[top+1]=g[u];
	for (int i=1;i<=top;i++) pre[i]=max(pre[i-1],f[stk[i]]+1);
	for (int i=top;i>=1;i--) suf[i]=max(suf[i+1],f[stk[i]]+1);
	for (int i=1;i<=top;i++) d[i]=max(pre[i-1],suf[i+1]);
	cur=lowf[u];
	for (int i=1;i<=top;i++) {
		int v=stk[i],res=f[v]+1,dis=d[i];
		int w=max(f[v]+1,low[v]-1);
		res>mx1?(mx2=mx1,mx1=res):(res>mx2?mx2=res:0);
		upd(g[v],dis+1);
		dnd(lowf[v],max(cur-1,dis+1));
		dnd(cur,w);
	}
	
	cur=lowf[u];
	for (int i=top;i>=1;i--) {
		int v=stk[i],dis=d[i];
		int w=max(f[v]+1,low[v]-1);
		dnd(lowf[v],max(cur-1,dis+1));
		dnd(cur,w);
	}
	low[u]=min(low[u],lowf[u]);
	high[u]=min(mx1-1,mx2+1);
}
int main()
{
	#ifdef Amberframe
		freopen("agc008f.in","r",stdin);
		freopen("agc008f.out","w",stdout);
	#endif
	scanf("%d",&n);
	for (int u,v,i=1;i<n;i++)
		scanf("%d %d",&u,&v),add(u,v);
	scanf("%s",s+1);dfs(1);
	for (int i=1;i<=n;i++) solve(pos[i]);
	for (int i=1;i<=n;i++)
		ans+=max(0,high[i]-low[i]+1);
	printf("%lld",ans+1);
	return 0;
}