#include <bits/stdc++.h>

using namespace std;

#define ll long long

inline ll read() {
    ll x = 0, f = 0; char ch = getchar();
    while (!isdigit(ch)) f = ch == '-', ch = getchar();
    while (isdigit(ch)) x = (x << 3) + (x << 1) + (ch ^ 48), ch = getchar();
    return f ? -x : x;
}

const int N = 5e5 + 10;
int n, q;
int w[N], fw[N], m;
int head[N], nex[N << 1], ver[N << 1], val[N << 1], tot = 1;
int fa[N][21], dep[N]; ll dis[N];
int d0[N], d1[N];

void add(int x, int y, int z) {
    ver[++tot] = y; val[tot] = z; nex[tot] = head[x]; head[x] = tot;
}

void dfs(int x, int father) {
    fa[x][0] = father; dep[x] = dep[father] + 1;
    for (int i = 1; i <= 20; ++i)
        fa[x][i] = fa[fa[x][i - 1]][i - 1];
    for (int i = head[x]; i; i = nex[i]) {
        int y = ver[i], z = val[i];
        if (y == father) continue;
        dis[y] = dis[x] + z;
        dfs(y, x);
    }
}

int lca(int x, int y) {
    if (dep[x] < dep[y]) swap(x, y); // dep[x] >= dep[y]
    int depth = dep[x] - dep[y];
    for (int j = 20; j >= 0; --j)
        if (depth >> j & 1) x = fa[x][j];
    if (x == y) return x;
    for (int j = 20; j >= 0; --j)
        if (fa[x][j] != fa[y][j]) x = fa[x][j], y = fa[y][j];
    return fa[x][0];
}

ll getdis(int x, int y) {
    if ((!x) || (!y)) return 0;
    int p = lca(x, y);
    // printf("x = %d, y = %d, p = %d, dis[x] = %lld, dis[y] = %lld, dis[p] = %lld; \n", x, y, p, dis[x], dis[y], dis[p]);
    return dis[x] + dis[y] - 2 * dis[p];
}

bool check(int g, int x, ll K) {
    // printf("check(%d, %d, %lld), getdis(%d, %d) = %lld, getdis(%d, %d) = %lld; \n", g, x, K, x, d0[g], getdis(x, d0[g]), x, d1[g], getdis(x, d1[g]));
    if (g == m) return false;
    if (getdis(x, d0[g]) <= K && getdis(x, d1[g]) <= K) return true;
    return false;
}

int main() {
    n = read(); q = read();
    for (int i = 1; i <= n; ++i) {
        w[i] = read() + 1;
        if (w[i] <= n) fw[w[i]] = i;
    }
    for (int i = 1; i < n; ++i) {
        int u = read(), v = read(), w = read();
        add(u, v, w); add(v, u, w);
    }
    dfs(1, 0);
    m = n + 1;
    for (int i = 1; i <= n; ++i) {
        if (!fw[i]) { m = i; break; }
    }
    for (int i = 1; i < m; ++i) {
        if (i == 1) d0[i] = fw[i];
        else if (i == 2) d0[i] = d0[i - 1], d1[i] = fw[i];
        else {
            ll dis0 = getdis(d0[i], fw[i]), dis1 = getdis(d1[i], fw[i]), dis2 = getdis(d0[i], d1[i]);
            if (dis2 > dis0 && dis2 > dis1) d0[i] = d0[i - 1], d1[i] = d1[i - 1];
            else if (dis0 > dis1) d0[i] = d0[i - 1], d1[i] = fw[i];
            else d0[i] = fw[i], d1[i] = d1[i - 1];
        }
        // printf("d0[%d] = %d, d1[%d] = %d; \n", i, d0[i], i, d1[i]);
    }
    while (q--) {
        int x = read(); ll K = read();
        int l = 1, r = m;
        while (l < r) {
            int mid = (l + r) >> 1;
            if (check(mid, x, K)) l = mid + 1;
            else r = mid;
        }
        printf("%d\n", l - 1);
    }
}