#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define ull unsigned long long
#define ld long double
#define bigint __int128
#define emb emplace_back
#define pb push_back
#define pii pair <int, int>
#define fi first
#define se second
#define all(v) v.begin(), v.end()
#define Task ""
#define MASK(k) (1ull << k)
#define bitcnt(k) __builtin_popcount(k)
#define testBit(n, k) ((n >> k) & 1)
#define flipBit(n, k) (n ^ (1ll << k))
#define offBit(n, k) (n & ~MASK(k))
#define onBit(n, k) (n | (1ll << k))
template <class T> bool minimize(T &a, T b) {if (a > b) {a = b; return true;} return false;}
template <class T> bool maximize(T &a, T b) {if (a < b) {a = b; return true;} return false;}
const int N = 1e5 + 5, LG = 17, mod = 1e9 + 7;
const ll INF = 1e18;
struct FenwickTree {
vector <ll> bit;
FenwickTree (int len) {
bit.assign(len + 1, 0);
}
void resize(int len) {
bit.assign(len + 1, 0);
}
void update(int p, int val) {
for (; p < bit.size(); p += p & -p)
bit[p] += val;
}
ll get(int p) {
ll res = 0; for (; p > 0; p -= p & -p) res += bit[p];
return res;
}
};
int n, m, q, par[N], h[N];
int st[N], en[N], up[N][LG], dfsTimes = 0;
pii edge[N];
vector <int> adj[N];
struct Query {
int u, v, x, y; pii range;
int cntSilver, checkPoints;
int lca;
} query[N];
void dfs(int u, int p = -1) {
st[u] = ++dfsTimes;
for (int v: adj[u]) if (v != p) {
par[v] = up[v][0] = u; h[v] = h[u] + 1;
for (int i = 1; i < LG; i++)
up[v][i] = up[up[v][i - 1]][i - 1];
dfs(v, u);
}
en[u] = ++dfsTimes;
}
int lca(int u, int v) {
if (h[u] != h[v]) {
if (h[u] < h[v]) swap(u, v);
for (int i = 0, k = h[u] - h[v]; (1 << i) <= k; i++)
if (testBit(k, i)) u = up[u][i];
}
if (u == v) return u;
for (int i = __lg(h[u]); i > -1; i--)
if (up[u][i] != up[v][i]) u = up[u][i], v = up[v][i];
return up[u][0];
}
int main() {
ios_base::sync_with_stdio(false); cin.tie(NULL); cout.tie(NULL);
if (fopen(Task".inp", "r")) {
freopen(Task".inp", "r", stdin);
freopen(Task".out", "w", stdout);
}
cin >> n >> m >> q;
for (int i = 1; i < n; i++) {
int u, v; cin >> u >> v;
adj[u].emplace_back(v);
adj[v].emplace_back(u);
edge[i] = make_pair(u, v);
}
vector <pii> checkPoints;
for (int i = 1; i <= m; i++) {
int p, c; cin >> p >> c;
checkPoints.emplace_back(c, p);
}
sort (all(checkPoints));
for (int i = 1; i <= q; i++) {
cin >> query[i].u >> query[i].v >> query[i].x >> query[i].y;
}
dfs(1);
for (int i = 1; i < n; i++) {
if (par[edge[i].fi] == edge[i].se)
swap(edge[i].fi, edge[i].se);
// edge[i] = make_pair(p, u)
}
FenwickTree fenCnt(2 * n), fenSum(2 * n);
for (auto [silver, e]: checkPoints) {
auto [p, u] = edge[e];
fenCnt.update(st[u], 1);
fenCnt.update(en[u], -1);
}
for (int i = 1; i <= q; i++) {
int u = query[i].u, v = query[i].v;
query[i].lca = lca(query[i].u, query[i].v);
query[i].range = make_pair(-1, checkPoints.size() - 1);
query[i].checkPoints = fenCnt.get(st[u]) + fenCnt.get(st[v]) - 2 * fenCnt.get(st[query[i].lca]);
query[i].cntSilver = 0;
}
while (true) {
vector <pii> events;
for (int i = 1; i <= q; i++) if (query[i].range.fi != query[i].range.se) {
int mid = (query[i].range.fi + query[i].range.se + 1) >> 1;
events.emplace_back(mid, i);
}
if (events.empty()) break;
sort (all(events));
int p = -1; fenSum.resize(2 * n), fenCnt.resize(2 * n);
for (auto [k, id]: events) {
while (p < k) {
auto [silver, e] = checkPoints[++p];
auto [p, u] = edge[e];
fenSum.update(st[u], silver);
fenSum.update(en[u], -silver);
fenCnt.update(st[u], 1);
fenCnt.update(en[u], -1);
}
int u = query[id].u, v = query[id].v;
ll silverCoins = fenSum.get(st[u]) + fenSum.get(st[v]) - 2 * fenSum.get(st[query[id].lca]);
if (silverCoins <= query[id].y) {
query[id].range.fi = k;
query[id].cntSilver = fenCnt.get(st[u]) + fenCnt.get(st[v]) - 2 * fenCnt.get(st[query[id].lca]);
}
else query[id].range.se = k - 1;
}
}
for (int i = 1; i <= q; i++) {
int useGold = query[i].checkPoints - query[i].cntSilver;
int ans = query[i].x - useGold;
if (ans < 0) ans = -1;
cout << ans << '\n';
}
}
