#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define pii pair<int,int>
#define fi first
#define se second
const int N = 1e6 + 5;
int n, m, q;
vector<pii> g[N];
vector<int> c[N];
int main() {
ios::sync_with_stdio(0);
cin.tie(0);
cin >> n >> m >> q;
for (int i = 1; i <= n - 1; i++) {
int u, v;
cin >> u >> v;
g[u].push_back({v, i});
g[v].push_back({u, i});
}
for (int i = 0; i < m; i++) {
int p; ll w;
cin >> p >> w;
c[p].push_back(w);
}
while (q--) {
int s, t; ll x, y;
cin >> s >> t >> x >> y;
vector<int> par(n + 1, -1), pe(n + 1, -1);
stack<int> st;
st.push(s);
par[s] = s;
while (!st.empty()) {
int u = st.top(); st.pop();
if (u == t) break;
for (auto e : g[u]) {
int v = e.first, id = e.second;
if (par[v] == -1) {
par[v] = u;
pe[v] = id;
st.push(v);
}
}
}
if (par[t] == -1) {
cout << -1 << "\n";
continue;
}
vector<ll> a;
int cur = t;
while (cur != s) {
for (ll w : c[pe[cur]]) a.push_back(w);
cur = par[cur];
}
sort(a.begin(), a.end());
ll sy = 0;
int cnt = 0;
for (ll w : a) {
if (sy + w <= y) {
sy += w;
cnt++;
} else break;
}
ll res = (ll)(a.size() - cnt);
if (res <= x) cout << x - res << '\n';
else cout << -1 << '\n';
}
}
