#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace std;
using namespace __gnu_pbds;
template<typename T> using ordered_set = tree<T,null_type,less_equal<T>,rb_tree_tag,
tree_order_statistics_node_update>;
#define ll long long
#define pi pair<int,int>
#define pb push_back
#define all(a) a.begin(),a.end()
const int mxn = 1e5+10;
vector<pi> g[mxn];
vector<ll> cost[mxn];
int par[mxn], head[mxn], heavy[mxn];
int pos[mxn], dep[mxn], val[mxn], cur_pos;
int inper[mxn];
int dfs(int u, int p){
par[u] = p, dep[u] = dep[p] + 1;
int sz = 1, mx = 0;
for(auto [v,i] : g[u]) if(v!=p){
int vsz = dfs(v,u); sz += vsz;
val[v] = i;
if(mx < vsz)
mx = vsz, heavy[u] = v;
}
return sz;
}
void decompose(int u, int h){
inper[cur_pos] = val[u];
head[u] = h, pos[u] = cur_pos++;
if(heavy[u]) decompose(heavy[u],h);
for(auto [v,i] : g[u]) if(v!=par[u] && v!=heavy[u])
decompose(v,v);
}
struct SegTree{
int sz; vector<ll> st[3*mxn];
vector<ll> pref[3*mxn];
void build(int i, int l, int r){
if(l==r){
st[i] = cost[inper[l]];
pref[i] = st[i];
for(int j = 1; j < st[i].size(); j++){
pref[i][j] += pref[i][j-1];
}
return;
}
int m = (l+r)>>1;
build(i<<1,l,m); build(i<<1|1,m+1,r);
merge(all(st[i<<1]),all(st[i<<1|1]),back_inserter(st[i]));
pref[i] = st[i];
for(int j = 1; j < st[i].size(); j++)
pref[i][j] += pref[i][j-1];
}
void init(int n){
sz = n;
build(1,0,sz-1);
}
pair<ll,ll> query(int i, int l, int r, int s, int e, ll x){
if(r < s || l > e) return {0ll,0ll};
if(s <= l && r <= e){
int ind = upper_bound(all(st[i]),x) - st[i].begin();
return {ind?pref[i][ind-1]:0ll , ind };
}
int m = (l+r)>>1;
auto s1 = query(i<<1,l,m,s,e,x);
auto s2 = query(i<<1|1,m+1,r,s,e,x);
return {s1.first + s2.first, s1.second + s2.second };
}
pair<ll,ll> query(int l, int r, ll x){
if(l > r) return {0ll,0ll};
return query(1,0,sz-1,l,r,x);
}
}st;
void apply(pair<ll,ll> &a, pair<ll,ll> b){
a.first = a.first + b.first;
a.second = a.second + b.second;
}
pair<ll,ll> query(int u, int v, ll mid){
pair<ll,ll> res = {0ll,0ll};
for(; head[u] != head[v]; v = par[head[v]]){
if(dep[head[u]] > dep[head[v]]) swap(u,v);
apply(res,st.query(pos[head[v]],pos[v],mid));
}
if(dep[u] > dep[v]) swap(u,v);
apply(res,st.query(pos[u]+1,pos[v],mid));
return res;
}
void solve(){
int n,m,q; scanf("%d %d %d",&n,&m,&q);
for(int i = 1; i < n; i++){
int u,v; scanf("%d %d",&u,&v);
g[u].pb({v,i});
g[v].pb({u,i});
}
for(int i = 0; i < m; i++){
int p,c; scanf("%d %d",&p,&c);
cost[p].pb(c);
}
for(int i = 1; i < n; i++)
sort(all(cost[i]));
dfs(1,1); decompose(1,1);
st.init(n);
while(q--){
int u,v; ll x,y;
scanf("%d %d %lld %lld",&u,&v,&x,&y);
ll l = 0, r = y+2;
while(l+1 < r){
ll mid = (l+r)>>1;
auto tmp = query(u,v,mid);
if(tmp.first <= y) l = mid;
else r = mid;
}
pair<ll,ll> res = query(u,v,l);
ll total = query(u,v,2e9).second;
total -= res.second; y -= res.first; total -= y / (l+1);
printf("%lld\n",max(-1ll,x - total));
}
}
int main(){
//freopen("censor.in","r",stdin);
//freopen("censor.out","w",stdout);
int t = 1;
while(t--) solve();
}
