#include <bits/stdc++.h>
#define int long long

using namespace std;

const int N = 1e6 + 10;

struct Line {
    int x, y, dis;
};

struct Que {
    int x, k, id;
};

int n, m;
Line stk[N];
vector<pair<int, int>> path[N];
int dis[N], dep[N], siz[N], fa[N], top[N], son[N];
int pos[N];
int w[N];
int maxn;
int ans[N];
Que q[N], tmp[N];

void dfs1(int u, int _fa) {
    fa[u] = _fa;
    dep[u] = dep[_fa] + 1;
    siz[u] = 1;
    for (auto it : path[u]) {
        int v = it.first, w = it.second;
        if (v == _fa) continue;
        dis[v] = dis[u] + w;
        dfs1(v, u);
        if (siz[v] > siz[son[u]]) son[u] = v;
    }
}

void dfs2(int u, int _top) {
    top[u] = _top;
    if (son[u]) dfs2(son[u], _top);
    for (auto it : path[u]) {
        int v = it.first;
        if (v == son[u] || v == fa[u]) continue;
        dfs2(v, v);
    }
}

int lca(int x, int y) {
    while (top[x] != top[y]) {
        if (dep[top[x]] < dep[top[y]]) swap(x, y);
        x = fa[top[x]];
    }
    return dep[x] < dep[y] ? x : y;
}

int getdis(int x, int y) {
    int l = lca(x, y);
    return dis[x] + dis[y] - 2 * dis[l];
}

// void solve(int l, int r, int L, int R) {
//     if (l == r) {
//         for (int i = L; i <= R; ++i) {
//             ans[q[i].id] = l;
//         }
//         return ;
//     }
//     int mid = (l + r) >> 1;
//     for (int i = l; i <= mid; ++i) {
//         if (i == 0) stk[i] = (Line){pos[i], pos[i], 0};
//         else stk[i] = merge(stk[i - 1], pos[i]);
//     }
//     for (int i = L; i <= R; ++i) tmp[i] = q[i];
//     int L1 = L, L2 = R;
//     for (int i = L; i <= R; ++i) {
//         if (Getdis(tmp[i].x, stk[mid]) <= tmp[i].k) {
//             q[L2] = tmp[i];
//             --L2;
//         }
//         else {
//             q[L1] = tmp[i];
//             ++L1;
//         }
//     }
    
//     // for (int i = L1; i <= )
//     // if (mid)
// }

Line merge(Line a, int b) {
    // if ()
    int dis1 = getdis(a.x, b);
    int dis2 = getdis(a.y, b);
    if (dis1 < a.dis && dis2 < a.dis) return a;
    if (dis1 > dis2) {
        a.y = b;
    }
    else {
        a.x = b;
    }
    return a;
}

signed main() {
    scanf("%lld%lld", &n, &m);
    for (int i = 1; i <= n; ++i) {
        scanf("%lld", &w[i]);
        if (w[i] <= n) {
            pos[w[i]] = i;
        }
    }
    for (int i = 0; i <= n + 2; ++i) {
        if (!pos[i]) {
            maxn = i;
            break;
        }
    }
    for (int i = 1; i < n; ++i) {
        int u, v, l;
        scanf("%lld%lld%lld", &u, &v, &l);
        path[u].emplace_back(v, l);
        path[v].emplace_back(u, l);
    }
    dfs1(1, 0);
    dfs2(1, 1);
    stk[0] = (Line){pos[0], pos[0], 0};
    for (int i = 1; i <= maxn; ++i) {
        stk[i] = merge(stk[i - 1], pos[i]);
    }
    for (int i = 1; i <= m; ++i) {
        int x, k;
        scanf("%lld%lld", &x, &k);
        int l = 0, r = maxn;
        while (l < r) {
            int mid = (l + r) >> 1;
            if (max(getdis(x, stk[mid].x), getdis(x, stk[mid].y)) <= k) l = mid + 1;
            else r = mid;
        }
        printf("%lld\n", l);
    }
    // for (i)
    // int l = 0, r = n;
    // solve(l, r, 1, m);
    return 0;
}