#include <bits/stdc++.h>
using namespace std;
using i64 = long long;
const int N = 1e6 + 10;

int n, q, ptr = 0, st[N], lg[N], dx[N], dy[N], dz[N];
i64 sp[N][20], d[N];
pair<i64, int> w[N];
vector<pair<i64, int>> e[N];

void dfs(int x, int p) {
    st[x] = ++ptr;  
    sp[ptr][0] = d[x];
    for (auto y : e[x]) {
        if (y.second == p)
            continue;
        d[y.second] = d[x] + y.first;
        dfs(y.second, x);
        sp[++ptr][0] = d[x];
    }
}

i64 dist(int u, int v) {
    i64 res = d[u] + d[v];
    u = st[u], v = st[v];
    if (u > v)
        swap(u, v);
    int k = lg[v - u + 1];
    i64 frog = min(sp[u][k], sp[v - (1 << k) + 1][k]);
    return res - frog * 2;
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    cin >> n >> q;
    for (int i = 1; i <= n; i++)
        cin >> w[i].first, w[i].second = i;

    for (int i = 1; i < n; i++) {
        int u, v, l;
        cin >> u >> v >> l;
        e[u].push_back({l, v}), e[v].push_back({l, u});
    }

    dfs(1, 0);

    for (int i = 2; i <= n * 2; i++)
        lg[i] = lg[i / 2] + 1;

    int m = n * 2 - 1;
    for (int i = 1; (1 << i) <= m; i++)
        for (int j = 1; j + (1 << i) <= m + 1; j++)
            sp[j][i] = min(sp[j][i - 1], sp[j + (1 << i - 1)][i - 1]);

    sort(w + 1, w + n + 1);

    int boss = 0;
    while (boss < n && w[boss + 1].first == boss)
        ++boss;

    if (!boss) {
        for (int i = 0; i < q; i++)
            cout << "0\n";
        return 0;
    }

    dx[1] = dy[1] = w[1].second, dz[1] = 0;
    for (int i = 2; i <= boss; i++) {
        i64 frog1 = dist(dx[i - 1], w[i].second);
        i64 frog2 = dist(dy[i - 1], w[i].second);
        if (frog1 > dz[i - 1] && frog1 > frog2) {
            dx[i] = dx[i - 1];
            dy[i] = w[i].second;
            dz[i] = frog1;
        }
        else if (frog2 > dz[i - 1] && frog2 >= frog1) {
            dy[i] = dy[i - 1];
            dx[i] = w[i].second;
            dz[i] = frog2;
        } else {
            dx[i] = dx[i - 1];
            dy[i] = dy[i - 1];
            dz[i] = dz[i - 1];
        }
    }

    for (int i = 0; i < q; i++) {
        int x;
        i64 d;
        cin >> x >> d;
        int l = 0, r = boss;
        while (l != r) {
            int mid = l + r + 1 >> 1;
            if (dist(x, dx[mid]) > d || dist(x, dy[mid]) > d)
                r = mid - 1;
            else
                l = mid;
        }
        cout << l << '\n';
    }
}