#include<cstdio>
#include<cstring>
#include<iostream>
#include<algorithm>
#define fo(i,l,r) for(int i=l;i<=r;i++)
#define of(i,l,r) for(int i=l;i>=r;i--)
#define fe(i,u) for(int i=head[u];i;i=e[i].next)
using namespace std;
typedef long long ll;
inline int rd()
{
    static int x,f;
    x=0,f=1;
    char ch=getchar();
    for(;ch<'0'||ch>'9';ch=getchar())if(ch=='-')f=-1;
    for(;ch>='0'&&ch<='9';ch=getchar())x=x*10+ch-'0';
    return x*f;
}
const int N=200010,Inf=1000000000;
struct edge{
    int v,next;
    edge(int v=0,int next=0):v(v),next(next){}
}e[N<<1];
int n;ll ans=0;
int head[N],tot=0;
int mx[N],sx[N],mn[N],siz[N];
char s[N];

inline void add(int u,int v){e[++tot]=edge(v,head[u]);head[u]=tot;}

void dfs1(int u,int fat)
{
    if(s[u]=='1')mn[u]=0,siz[u]=1;
    else mn[u]=Inf;
    fe(i,u){
        int v=e[i].v;
        if(v==fat)continue;
        dfs1(v,u);siz[u]+=siz[v];
        int dis=mx[v]+1;
        if(mx[u]<dis)sx[u]=mx[u],mx[u]=dis;
        else sx[u]=max(sx[u],dis);
        if(siz[v])mn[u]=min(mn[u],dis);
    }
}
void dfs2(int u,int fat)
{
    int mxd=min(mx[u]-1,sx[u]+1);
    if(mxd>=mn[u])ans+=(ll)mxd-mn[u]+1;
    fe(i,u){
        int v=e[i].v;
        if(v==fat)continue;
        int dis=mx[u]==mx[v]+1?sx[u]+1:mx[u]+1;
        if(mx[v]<dis)sx[v]=mx[v],mx[v]=dis;
        else sx[v]=max(sx[v],dis);
        if(siz[v]<siz[1])mn[v]=min(mn[v],dis);
        dfs2(v,u);
    }
}

int main()
{
    n=rd();
    fo(i,1,n-1){
        int x=rd(),y=rd();
        add(x,y);add(y,x);
    }
    scanf("%s",s+1);
    dfs1(1,0);dfs2(1,0);
    printf("%lld\n",ans+1ll);
    return 0;
}