#include <bits/stdc++.h>
#define dbg(x) cerr << #x << " = " << x << "\n"
#define fast_io ios_base::sync_with_stdio(0); cin.tie(0); cout.tie()
using namespace std;
using ll = long long;
using ld = long double;
const int N = 1e6 + 100;
ll a[N], ap, aq, mx[N], mx1[N], mx2[N];
int n;
vector <int> g[N];
bool smaller(ll x, ll y) { return (x * aq) < (y * ap); }
void dfs(int v, int pr) {
for (int u : g[v]) {
if (u == pr)
continue;
dfs(u, v);
if (mx[u] > mx1[v]) swap(mx1[v], mx2[v]), mx1[v] = mx[u];
else if (mx[u] > mx2[v]) mx2[v] = mx[u];
}
if (a[v] == 1) mx[v] = mx1[v] + 1;
else mx[v] = 0;
}
void dfs(int v, int pr, ll cur) {
for (int u : g[v]) {
if (u == pr)
continue;
ll cr = 0;
if (a[v] == 1) {
if (mx[u] == mx1[v]) cr = max(cur + 1, mx2[v] + 1);
else cr = max(cur + 1, mx1[v] + 1);
}
dfs(u, v, cr);
}
ll a1 = mx1[v], a2 = mx2[v];
if (cur > a1) swap(a1, a2), a1 = cur;
else if (cur > a2) a2 = cur;
if (smaller(a[v], a1 + a2 + 1)) {
ap = a[v];
aq = a1 + a2 + 1;
}
}
int main() {
fast_io;
cin >> n;
for (int i = 0; i < n - 1; ++i) {
int v, u;
cin >> v >> u;
--v, --u;
g[v].push_back(u);
g[u].push_back(v);
}
for (int i = 0; i < n; ++i)
cin >> a[i];
if (*min_element(a, a + n) > 1)
return void(cout << *min_element(a, a + n) << "/1\n"), 0;
ap = aq = 1;
dfs(0, 0);
dfs(0, 0, 0);
ll gc = __gcd(ap, aq);
cout << ap / gc << "/" << aq / gc << "\n";
}
