#include <bits/stdc++.h>
using namespace std;
#define ll long long
const int nx=1e5+5, kx=17;
ll n, m, q, u, v, p, c, lvl[nx], pa[nx][kx], sp, tp, x, y;
vector<pair<ll, ll>> d[nx], t, s[nx];
bool vs[nx];
void dfs(int u, int p)
{
pa[u][0]=p; lvl[u]=lvl[p]+1;
for (int i=1; i<kx; i++) pa[u][i]=pa[pa[u][i-1]][i-1];
for (auto [v, idx]:d[u]) if (v!=p) dfs(v, u);
}
int lca(int u, int v)
{
if (lvl[u]>lvl[v]) swap(u, v);
for (int i=kx-1; i>=0; i--) if (lvl[u]<=lvl[pa[v][i]]) v=pa[v][i];
if (u==v) return u;
for (int i=kx-1; i>=0; i--) if (pa[u][i]!=pa[v][i]) u=pa[u][i], v=pa[v][i];
return pa[u][0];
}
struct persist
{
struct node
{
ll sm, f;
node *l, *r;
node(): sm(0), f(0), l(0), r(0){}
};
typedef node* pnode;
pnode rt[nx];
void build(int l, int r, pnode &t)
{
t=new node();
if (l==r) return;
int md=(l+r)/2;
build(l, md, t->l);
build(md+1, r, t->r);
t->f=t->l->f+t->r->f;
t->sm=t->l->sm+t->r->sm;
}
void update(int l, int r, pnode &t, pnode k, int idx, ll val)
{
t=new node(*k);
if (l==r) return t->f=1, t->sm=val, void();
int md=(l+r)/2;
if (idx<=md) update(l, md, t->l, k->l, idx, val);
else update(md+1, r, t->r, k->r, idx, val);
t->f=t->l->f+t->r->f;
t->sm=t->l->sm+t->r->sm;
}
ll query(int l, int r, pnode s, pnode t, pnode lc, ll am)
{
//printf("%d %d %d\n", l, r, am);
if (l==r) return (s->sm+t->sm-2*lc->sm<=am)?(s->f+t->f-2*lc->f):0;
int md=(l+r)/2;
ll usel=s->l->sm+t->l->sm-2*(lc->l->sm);
if (usel<=am) return s->l->f+t->l->f-2*lc->l->f+query(md+1, r, s->r, t->r, lc->r, am-usel);
return query(l, md, s->l, t->l, lc->l, am);
}
} st;
void dfs2(int u, int p)
{
for (auto [v, idx]:d[u])
{
if (v==p) continue;
st.rt[v]=st.rt[u];
for (auto [vl, idx2]:s[idx]) st.update(1, m, st.rt[v], st.rt[v], idx2, vl);
dfs2(v, u);
}
}
int main()
{
cin.tie(NULL)->sync_with_stdio(false);
cin>>n>>m>>q;
for (int i=1; i<=n-1; i++) cin>>u>>v, d[u].push_back({v, i}), d[v].push_back({u, i});
for (int i=1; i<=m; i++) cin>>p>>c, t.push_back({c, p});
sort(t.begin(), t.end());
for (int i=0; i<m; i++) s[t[i].second].push_back({t[i].first, i+1});
dfs(1, 1);
st.build(1, m, st.rt[1]);
dfs2(1, 1);
while (q--)
{
cin>>sp>>tp>>x>>y;
int lc=lca(sp, tp);
//printf("%d %d %d\n", st.rt[sp], st.rt[tp], st.rt[lc]);
ll gu=st.query(1, m, st.rt[sp], st.rt[tp], st.rt[lc], y);
ll tc=st.rt[sp]->f+st.rt[tp]->f-2*st.rt[lc]->f;
if (tc-gu>x) cout<<-1<<'\n';
else cout<<x-(tc-gu)<<'\n';
}
}
