#include <bits/stdc++.h>

using namespace std;

typedef long long ll;

constexpr int N = 1e5 + 10, K = 17;

int n, m, q, w[N], rt[N], dep[N], fa[N][K];

struct Edge {
    int u, v;
} e[N];

vector<int> G[N], H[N];

inline void add(int u, int v) {G[u].emplace_back(v), G[v].emplace_back(u);}

namespace PST {
    int tot;

    struct Seg {
        ll w; int sz, ls, rs;
    } t[N * 40];

    int newt(int pos) {t[++tot] = t[pos]; return tot;}

    void upd(int &pos, int l, int r, int x) {
        t[pos = newt(pos)].w += x, t[pos].sz++;
        if (l == r) return; int mid = (l + r) >> 1;
        x <= mid ? upd(t[pos].ls, l, mid, x) : upd(t[pos].rs, mid + 1, r, x);
    }

    int query(int u, int v, int lca, int l, int r, ll c) {
        if (l == r) return min(c / l, (ll)t[u].sz + t[v].sz - 2 * t[lca].sz);
        int lsz = t[t[u].ls].sz + t[t[v].ls].sz - 2 * t[t[lca].ls].sz;
        ll tmp = t[t[u].ls].w + t[t[v].ls].w - 2 * t[t[lca].ls].w;
        int mid = (l + r) >> 1;
        if (tmp > c) return query(t[u].ls, t[v].ls, t[lca].ls, l, mid, c);
        return lsz + query(t[u].rs, t[v].rs, t[lca].rs, mid + 1, r, c - tmp);
    }
}

void dfs(int u) {
    for (int k = 1; k < K; k++) fa[u][k] = fa[fa[u][k - 1]][k - 1];
    for (int v : G[u]) if (v != fa[u][0]) fa[v][0] = u, dep[v] = dep[u] + 1, dfs(v);
}

void dfs2(int u) {
    w[u] += H[u].size(), rt[u] = rt[fa[u][0]];
    for (int c : H[u]) PST::upd(rt[u], 1, 1e9, c);
    for (int v : G[u]) if (v != fa[u][0]) w[v] += w[u], dfs2(v);
}

int LCA(int u, int v) {
    if (dep[u] < dep[v]) swap(u, v);
    for (int k = 16; k >= 0; k--) if (dep[fa[u][k]] >= dep[v]) u = fa[u][k];
    if (u == v) return u;
    for (int k = 16; k >= 0; k--) if (fa[u][k] != fa[v][k]) u = fa[u][k], v = fa[v][k];
    return fa[u][0];
}

int main() {
    ios_base::sync_with_stdio(0); cin.tie(nullptr), cout.tie(nullptr);
    cin >> n >> m >> q;
    for (int i = 1; i < n; i++) cin >> e[i].u >> e[i].v, add(e[i].u, e[i].v);
    dfs(1);
    for (int i = 1, id, c; i <= m; i++) {
        cin >> id >> c;
        if (dep[e[id].u] < dep[e[id].v]) swap(e[id].u, e[id].v);
        H[e[id].u].emplace_back(c);
    }
    dfs2(1);
    while (q--) {
        int s, t, x; ll y; cin >> s >> t >> x >> y;
        int lca = LCA(s, t), rest = x - (w[s] + w[t] - 2 * w[lca] - PST::query(rt[s], rt[t], rt[lca], 1, 1e9, y));
        cout << max(-1, rest) << '\n';
    }
    return 0;
}