#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define all(aaa) aaa.begin(), aaa.end()
const int N = 1e6 + 5, INF = 1e9;
vector<int> g[N];
int x[N], dp[N];
ll p, q;
void dfs(int node, int anc) {
if (anc != -1)
g[node].erase(find(all(g[node]), anc));
for (int to : g[node]) {
dfs(to, node);
dp[node] = max(dp[node], dp[to]);
}
if (x[node] == 1)
dp[node]++;
else
dp[node] = 0;
}
void upd(ll x, ll y) {
if (p * y > x * q) {
p = x;
q = y;
}
}
void deep(int node, int up) {
sort(all(g[node]), [=](int x, int y) {
return dp[x] > dp[y];
});
if (x[node] < 3) {
if (g[node].size() > 0) {
upd(x[node], up + dp[g[node][0]] + 1);
}
if (g[node].size() > 1) {
upd(x[node], dp[g[node][0]] + dp[g[node][1]] + 1);
}
}
for (int to : g[node]) {
int nup = 0;
if (x[node] == 1) {
int cur = dp[g[node][0]];
if (to == g[node][0])
cur = g[node].size() > 1 ? dp[g[node][1]] : 0;
nup = max(up, cur) + 1;
}
deep(to, nup);
}
}
signed main() {
#ifdef HOME
freopen("input.txt", "r", stdin);
freopen("output.txt", "w", stdout);
#endif
ios_base::sync_with_stdio(0);
cin.tie(0);
int n;
cin >> n;
for (int i = 0; i < n - 1; i++) {
int a, b;
cin >> a >> b;
a--, b--;
g[a].push_back(b);
g[b].push_back(a);
}
for (int i = 0; i < n; i++) {
cin >> x[i];
}
p = *min_element(x, x + n), q = 1;
dfs(0, -1);
deep(0, 0);
if (q % p == 0) {
q /= p;
p = 1;
}
cout << p << "/" << q;
return 0;
}
