#include <iostream>
#include <cstdio>
#include <algorithm>
#include <vector>
using namespace std;
#define endl '\n'
#define ll long long
#define pi pair<ll, ll>
#define f first
#define s second
const int mxn = 1000000;
int n;
int a[mxn], f1[mxn], f2[mxn];
vector<int> g[mxn];
void upd(int x, int v){
f2[x] = max(f2[x], v);
if(f2[x] > f1[x]) swap(f1[x], f2[x]);
}
void dfs(int c, int p){
for(int i : g[c]){
if(i == p) continue;
dfs(i, c);
if(!~-a[i]) upd(c, f1[i] + 1);
}
}
void dfs2(int c, int p){
for(int i : g[c]){
if(i == p) continue;
if(!~-a[c]) upd(i, (f1[i] + 1 == f1[c] ? f2[c] : f1[c]) + 1);
dfs2(i, c);
}
}
int main(){
ios::sync_with_stdio(0);
cin.tie(0);
cin >> n;
for(int i = 0; i < n - 1; i++){
int u, v;
cin >> u >> v;
u--, v--;
g[u].push_back(v);
g[v].push_back(u);
}
for(int i = 0; i < n; i++) cin >> a[i];
dfs(0, -1);
dfs2(0, -1);
ll x = 1, y = 0;
for(int i = 0; i < n; i++){
ll w = a[i], z = f1[i] + f2[i] + 1;
if(w * y < x * z) x = w, y = z;
}
ll g = __gcd(x, y);
x /= g, y /= g;
cout << x << "/" << y << endl;
return 0;
}
