PWALK

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

using ll = long long;
using pii = pair<ll, int>;
using tpii = tuple<int, int, int>;

const int maxN = 1e5 + 5;
const ll INF = 1e18 + 7;
const int MOD = 1e9 + 7;

int n, nTest;
vector<pii> graph[maxN];

ll d[maxN];

void Dijkstra(int s, int t) {
    fill(d + 1, d + n + 1, INF);
    d[s] = 0;
    priority_queue<pii, vector<pii>, greater<pii>> pq;
    pq.push({0, s});

    while (!pq.empty()) {
        const auto [du, u] = pq.top(); pq.pop();

        if (d[u] > du) continue;

        for (const auto &[uv, v] : graph[u]) {
            if (d[v] > d[u] + uv) {
                d[v] = d[u] + uv;
                pq.push({d[v], v});
            }
        }
    }
}

int main() {
#ifdef LOCAL
    freopen("in1.txt", "r", stdin);
#else
    freopen("PWALK.inp", "r", stdin);
    freopen("PWALK.out", "w", stdout);
#endif
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);

    cin >> n >> nTest;
    for (int i = 1; i <= n-1; i++) {
        int u, v, w; cin >> u >> v >> w;
        graph[u].push_back({w, v});
        graph[v].push_back({w, u});
    }

    for (int i = 1; i <= nTest; ++i) {
        int u, v; cin >> u >> v;
        Dijkstra(u, v);
        cout << d[v] << '\n';
    }

    return 0;
}