#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define ld long double
#define FOR(i,l,r) for(int i = (l), _r = (r); i <= _r; i++)
#define FORNG(i,r,l) for(int i = (r), _l = (l); i >= _l; i--)
#define REP(i,r) for(int i = 0, _r = (r); i < _r; i++)
#define endl '\n'
#define fi first
#define se second
#define pb push_back
#define size(v) ((ll)(v).size())
#define all(v) (v).begin(),(v).end()
#define MASK(x) (1LL << (x))
#define BIT(x,i) (((x) >> (i)) & 1)
const ll MOD = 1e9 + 7, N = 2e5 + 36, LOG = 18;
const int INF = 1e9 + 36;
ll n,m,q,par[N],high[N];
vector<int> adj[N];
vector<ll> S[N];
pair<int,int> edge[N];
void dfs(int u){
for(int v : adj[u])if(v != par[u]){
high[v] = high[u] + 1;
par[v] = u;
dfs(v);
}
}
int main(){
//freopen(".INP", "r", stdin);
//freopen(".OUT", "w", stdout);
ios_base::sync_with_stdio(0);cin.tie(0);
cin>>n>>m>>q;
FOR(i,1,n-1){
int u,v;cin>>u>>v;
edge[i] = {u, v};
adj[u].pb(v);
adj[v].pb(u);
}
dfs(1);
FOR(i,1,m){
ll p,c;cin>>p>>c;
auto [u, v] = edge[p];
if(high[u] > high[v])S[u].pb(c);
else S[v].pb(c);
}
FOR(i,1,q){
ll s,t,x,y;cin>>s>>t>>x>>y;
vector<ll> vec;
if(high[s] < high[t])swap(s, t);
ll sum = 0;
while(high[s] < high[t]){
for(ll v : S[s])vec.pb(v),sum += v;
s = par[s];
}
while(s != t){
for(ll v : S[s])vec.pb(v),sum += v;
for(ll v : S[t])vec.pb(v),sum += v;
s = par[s];
t = par[t];
}
sort(all(vec), greater<ll>());
for(ll v : vec){
if(sum <= y)break;
x--;
sum -= v;
}
if(x < 0)cout<<-1<<endl;
else cout<<x<<endl;
}
}
