#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define MAXN 1000005
#define FOR(i, a, b) for(ll i = a; i <= b; i++)
ll n, m[MAXN], dp[MAXN][2];
vector<ll> adj[MAXN];
pair<ll, ll> r = {-1, -1};
void dfs(ll v, ll p){
dp[v][0] = dp[v][1] = -1;
ll z1 = -1, z2 = -1, o1 = -1, o2 = -1;
ll idz = -1, ido = -1;
for(ll v2 : adj[v]) if(v2 != p) {
dfs(v2, v);
if(m[v] >= 3) continue;
if(dp[v2][0] != -1){
if(m[v] == 2){
dp[v][1] = max(dp[v][1], dp[v2][0] + 1);
if(r.first == -1 || r.first * dp[v][1] > 2 * r.second){
r = {2, dp[v][1]};
}
}else if(m[v] == 1){
dp[v][0] = max(dp[v][0], dp[v2][0] + 1);
if(r.first == -1 || r.first * dp[v][0] > r.second){
r = {1, dp[v][0]};
}
}
if(dp[v2][0] > z1) {
z2 = z1;
z1 = dp[v2][0], idz = v2;
}else if(dp[v2][0] > z2){
z2 = dp[v2][0];
}
}
if(dp[v2][1] != -1){
if(m[v] == 1){
dp[v][1] = max(dp[v][1], dp[v2][1] + 1);
if(r.first == -1 || r.first * dp[v][1] > 2 * r.second){
r = {2, dp[v][1]};
}
}
if(dp[v2][1] > o1) {
o2 = o1;
o1 = dp[v2][1], ido = v2;
}else if(dp[v2][1] > o2){
o2 = dp[v2][1];
}
}
}
if(m[v] == 1){
// 2 on one side, 1 on the other -- MAY CONFLICT
if(ido != idz){
if((z1 != -1 && o1 != -1) && (r.first == -1 || r.first * (1 + z1 + o1) > 2 * r.second)){
r = {2, 1 + z1 + o1};
}
}else{
if((z1 != -1 && o2 != -1) && (r.first == -1 || r.first * (1 + z1 + o2) > 2 * r.second)){
r = {2, 1 + z1 + o2};
}
if((z2 != -1 && o1 != -1) && (r.first == -1 || r.first * (1 + z2 + o1) > 2 * r.second)){
r = {2, 1 + z2 + o1};
}
}
// 1 on both sides -- NO CONFLICT
if((z1 != -1 && z2 != -1) && (r.first == -1 || r.first * (1 + z1 + z2) > r.second)){
r = {1, 1 + z1 + z2};
}
// start own dp[v][0]
dp[v][0] = max(dp[v][0], 1ll);
}
if(m[v] == 2){
// 1 on both sides -- NO CONFLICT
if((z1 != -1 && z2 != -1) && (r.first == -1 || r.first * (1 + z1 + z2) > 2 * r.second)){
r = {2, 1 + z1 + z2};
}
// start own dp[v][1]
dp[v][1] = max(dp[v][1], 1ll);
}
if(m[v] >= 3){
if(r.first == -1 || r.first > m[v] * r.second){
r = {m[v], 1};
}
}
}
int main(){
cin >> n;
FOR(i, 1, n - 1) {
ll a, b;
cin >> a >> b;
adj[a].push_back(b);
adj[b].push_back(a);
}
FOR(i, 1, n) cin >> m[i];
dfs(1, -1);
if(r.first == 2 && r.second % 2 == 0) r.first /= 2, r.second /= 2;
cout << r.first << "/" << r.second << endl;
}
