#include <bits/stdc++.h>
using namespace std;
const int N = 200010, INF = 0x3f3f3f3f;
struct edge {
  int la,b;
} con[N << 1];
int tot,fir[N];
void add(int from,int to) {
  con[++tot] = (edge) {fir[from],to};
  fir[from] = tot;
}
int n,mxdep[N][2],hson[N],sz[N],low[N];
char s[N];
long long ans;
void dfs(int pos,int fa) {
  sz[pos] = s[pos] - '0';
  mxdep[pos][0] = 0;
  mxdep[pos][1] = - INF;
  hson[pos] = 0;
  for (int i = fir[pos] ; i ; i = con[i].la) {
    if (con[i].b == fa) continue;
    dfs(con[i].b,pos);
    sz[pos] += sz[con[i].b];
    if (mxdep[con[i].b][0] > mxdep[hson[pos]][0] || (!hson[pos]))
      hson[pos] = con[i].b;
    if (mxdep[con[i].b][0]+1 > mxdep[pos][0]) {
      mxdep[pos][1] = mxdep[pos][0];
      mxdep[pos][0] = mxdep[con[i].b][0] + 1;
    } else mxdep[pos][1] = max(mxdep[pos][1],mxdep[con[i].b][0] + 1);
    if (sz[con[i].b]) low[pos] = min(low[pos],mxdep[con[i].b][0] + 1);
  }
}
void fsd(int pos,int fa) {
  for (int i = fir[pos] ; i ; i = con[i].la) {
    if (con[i].b == fa) continue;
    int val = (con[i].b == hson[pos] ? mxdep[pos][1] : mxdep[pos][0]) + 1;
    if (val > mxdep[con[i].b][0]) {
      mxdep[con[i].b][1] = mxdep[con[i].b][0];
      mxdep[con[i].b][0] = val;
      hson[con[i].b] = pos;
    } else mxdep[con[i].b][1] = max(mxdep[con[i].b][1],val);
    if (sz[1] - sz[con[i].b] > 0)
      low[con[i].b] = min(low[con[i].b],val);
    fsd(con[i].b,pos);
  }
}
int main() {
  int x,y;
  scanf("%d",&n);
  for (int i = 1 ; i < n ; ++ i) {
    scanf("%d%d",&x,&y);
    add(x,y);
    add(y,x);
  }
  scanf("%s",s+1);
  memset(low,0x3f,sizeof low);
  dfs(1,0);
  fsd(1,0);
  for (int i = 1 ; i <= n ; ++ i) {
    int tmp = mxdep[i][1] + 1;
    if (mxdep[i][0] > mxdep[i][1] + 1)
      ++ tmp;
    if (mxdep[i][0] == mxdep[i][1]) -- tmp;
    if (s[i] - '0' == 0) tmp -= low[i];
    ans += max(tmp,0);
  }
  printf("%lld\n",ans+1);
  return 0;
}
