#include <bits/stdc++.h>
using namespace std;
#define int long long
#define sz(x) (int)x.size()
const int maxn = 1E5+8;
vector<pair<int, vector<int>>> adj[maxn];
struct edge {
int u, v;
vector<int> c;
};
vector<edge> edges;
map<pair<int, int>, int> mp;
int n, m, q, ls[maxn];
void dfs(int u, int pr = -1) {
for (auto& [v, c] : adj[u]) {
if (v == pr) continue;
dfs(v, u);
ls[v] = u;
}
}
int32_t main() {
ios::sync_with_stdio(0); cin.tie(0);
cin >> n >> m >> q;
for (int i = 0; i < n - 1; i++) {
int u, v;
cin >> u >> v;
edges.push_back((edge) {u, v, {}});
mp[{u, v}] = mp[{v, u}] = i;
}
for (int i = 1; i <= m; i++) {
int p, c;
cin >> p >> c;
edges[p-1].c.push_back(c);
}
for (auto& [u, v, c] : edges) {
adj[u].push_back({v, c});
adj[v].push_back({u, c});
}
while (q--) {
int s, t, x, y;
cin >> s >> t >> x >> y;
for (int i = 1; i <= n; i++) ls[i] = -1;
vector<int> path, c;
dfs(s);
int bk = t;
while (bk != -1) {
path.push_back(bk);
bk = ls[bk];
}
reverse(path.begin(), path.end());
// for (int& e : path) cout << e << " ";
// cout << "\n";
for (int i = 0; i < sz(path) - 1; i++) {
int l = path[i], r = path[i+1];
for (int& e : edges[mp[{l, r}]].c) c.push_back(e);
}
sort(c.begin(), c.end());
int cur = 0, mnd = sz(c);
for (int i = 0; i < sz(c); i++) {
cur += c[i];
if (cur <= y) {
int d = sz(c) - i - 1;
mnd = min(mnd, d);
}
}
if (x < mnd) {
cout << "-1\n";
goto bye;
}
cout << x - mnd << "\n";
bye:{}
}
}
