#include <bits/stdc++.h>
using namespace std;
vector<int> depth;
vector<int> val;
void dfs (vector<int>& tot, vector<vector<int> >& adj, vector<bool> &hasVisited, int curNode, int prevNode) {
if (val[curNode] != 1) {
return;
}
if (curNode == prevNode) {
depth[curNode] = 0;
} else {
depth[curNode] = depth[prevNode] + 1;
}
hasVisited[curNode] = true;
for (int i: adj[curNode]) {
if (i != prevNode) {
dfs (tot, adj, hasVisited, i, curNode);
}
}
tot.push_back(curNode);
}
int main() {
vector<vector<int> > adj;
int n;
cin >> n;
adj.resize(n), depth.resize(n);
for (int i = 0; i < n - 1; i++) {
int u, v;
cin >> u >> v;
u--, v--;
adj[u].push_back(v), adj[v].push_back(u);
}
val.resize(n);
int myMin = INT_MAX;
for (int i = 0; i < n; i++) {
cin >> val[i];
myMin = min(myMin, val[i]);
}
if (myMin >= 2) {
cout << myMin << "/" << 1;
return 0;
}
vector<bool> hasVisited;
hasVisited.assign(n, false);
int myMax = 0;
for (int i = 0; i < n; i++) {
if (hasVisited[i] || val[i] != 1) {
continue;
}
vector<int> tot;
dfs (tot, adj, hasVisited, i, i);
pair<int,int> p = make_pair(-1, -1);
for (int j: tot) {
p = max(p, make_pair(depth[j], j));
}
int u = p.second;
p = make_pair(-1, -1);
tot.clear();
dfs (tot, adj, hasVisited, u, u);
for (int j: tot) {
p = max(p, make_pair(depth[j], j));
}
int v = p.second;
myMax = max(myMax, abs(depth[u] - depth[v]) + 1);
}
cout << 1 << "/" << myMax;
}
