#include <bits/stdc++.h>
using namespace std;
vector<int>checks;
void dfs(int st, vector<array<int,2>>g[], vector<int>costs[], vector<int>&curr, int tar, int p){
if(st==tar){
for(int i : curr){
checks.push_back(i);
}
return;
}
for(array<int,2>e:g[st]){
if(e[0]==p)
continue;
for(int i : costs[e[1]]){
curr.push_back(i);
}
dfs(e[0],g,costs,curr,tar,st);
for(int i : costs[e[1]]){
assert(curr.size());
curr.pop_back();
}
}
}
signed main(){
ios::sync_with_stdio(0);
cin.tie(0);
int n,m,q;
cin >> n >> m >> q;
vector<array<int,2>>g[n];
for(int i = 0;i<n-1;i++){
int a,b;
cin >> a >> b;
a--;b--;
g[a].push_back({b,i});
g[b].push_back({a,i});
}
vector<int>costs[n-1];
for(int i = 0;i<m;i++){
int p,c;
cin >> p >> c;
p--;
costs[p].push_back(c);
}
for(int i = 0;i<n-1;i++){
if(costs[i].size())
sort(costs[i].begin(),costs[i].end());
}
while(q--){
int s,t,x,y;
cin >> s >> t >> x >> y;
s--;t--;
checks.clear();
vector<int>temp;
dfs(s,g,costs,temp,t,-1);
if(checks.size()!=0){
sort(checks.begin(),checks.end());
x-=checks.size();
for(int i : checks){
if(y-i>=0){
y-=i;
x++;
}
else{
break;
}
}
}
if(x<0){
cout << -1 << "\n";
}
else{
cout << x << "\n";
}
}
return 0;
}
