#include <bits/stdc++.h>
using namespace std;

struct Edge {
    int u;
    int v;
    int cost;
    Edge(int a, int b, int c) : u(a), v(b), cost(c) {

    }
};
using Graph = vector<vector<Edge>>;

vector<int> depth;
vector<long long> subtree_size;
void dfs(const Graph& G, int v, int p, int d) {
    depth[v] = d;
    for (auto nv : G[v]) {
        if (nv.v == p) continue;
        dfs(G, nv.v, v, d + 1);
    }

    subtree_size[v] = 1;
    for (auto c : G[v]) {
        if (c.v == p) continue;
        subtree_size[v] += subtree_size[c.v];
    }
}

int main() {
    long long N, Q; cin >> N >> Q;

    Graph G(N);
    for (int i = 0; i < N - 1; i++) {
        int a, b;
        cin >> a >> b;
        G[a - 1].emplace_back(a - 1, b - 1, 1);
        G[b - 1].emplace_back(b - 1, a - 1, 1);
    }

    depth.assign(N, 0);
    subtree_size.assign(N, 0);

    dfs(G, 0, -1, 0);

    long long ans = 0;
    for (int i = 0; i < Q; i++) {
        long long p, x; cin >> p >> x;
        ans += subtree_size[p - 1] * x;
    }
}