#include <bits/stdc++.h>
using namespace std;
const int N = 300000;
#define LL long long
LL ans;
int n;
vector <int> bi[N];
char s[N];
int mxl[N], m2l[N];
int mns[N], vs[N];
void dfs1(int t, int f)
{
    if (s[t] == '1') vs[t] = 1; mns[t] = 1e9;
    for (int i = 0; i < bi[t].size(); ++ i)
        if (bi[t][i] != f)
        {
            dfs1(bi[t][i], t);
            if (mxl[bi[t][i]] + 1 >= mxl[t]) m2l[t] = mxl[t], mxl[t] = mxl[bi[t][i]] + 1;
            else if (mxl[bi[t][i]] + 1 >= m2l[t]) m2l[t] = mxl[bi[t][i]] + 1;
            if (vs[bi[t][i]] && mxl[bi[t][i]] + 1 <= mns[t]) mns[t] = mxl[bi[t][i]] + 1;
            vs[t] += vs[bi[t][i]];
        }
}
void dfs2(int t, int f, int w, int u)
{
    int nmx = mxl[t], nm2 = m2l[t];
    if (w >= nmx) nm2 = nmx, nmx = w;
    else if (w >= nm2) nm2 = w;
    int vvv = mns[t]; if (s[t] == '1') vvv = 0;
    if (u) vvv = min(vvv, w);
    int res = max(0, nmx + 1 - max(1, nmx - nm2 - 1) - vvv);
    ans += res;
    for (int i = 0; i < bi[t].size(); ++ i)
        if (bi[t][i] != f)
            dfs2(bi[t][i], t, max(w, mxl[t] == mxl[bi[t][i]] + 1? m2l[t]: mxl[t]) + 1, u + vs[t] - vs[bi[t][i]]);
}
int main()
{
    scanf("%d", &n);
    for (int i = 1; i < n; ++ i)
    {
        int a, b;
        scanf("%d%d", &a, &b);
        bi[a].push_back(b);
        bi[b].push_back(a);
    }
    scanf("%s", s + 1);
    ans = 1;
    dfs1(1, 1);
    dfs2(1, 1, 0, 0);
    printf("%lld\n", ans);
}
