#include <bits/stdc++.h>
using namespace std;
typedef long long LL;
const int N = 5e5 + 10, L = 21;
int n, q, fth[N], a[N], b[N], dep[N], stg[N * 2], lm, in[N], ord[N * 2];
int tot, to[N * 2], nxt[N * 2], fst[N], wei[N * 2], up;
LL dis[N];
void add(int ui, int vi, int wi)
{
    to[++tot] = vi, wei[tot] = wi, nxt[tot] = fst[ui];
    fst[ui] = tot;
}
struct ST
{
    int f[L][N * 2], Lg[N * 2], *ay;
    void build(int *ary, int ln)
    {
        ay = ary;
        Lg[0] = -1;
        for (int i = 1; i <= ln; i++)
            Lg[i] = Lg[i >> 1] + 1;
        int p1, p2;
        iota(f[0] + 1, f[0] + ln + 1, 1);
        for (int j = 1; 1 << j <= ln; j++)
            for (int i = 1; i + (1 << j) - 1 <= ln; i++)
            {
                p1 = f[j - 1][i], p2 = f[j - 1][i + (1 << j - 1)];
                if (ary[p1] > ary[p2])
                    f[j][i] = p2;
                else
                    f[j][i] = p1;
            }
    }
    int ask(int l, int r)
    {
        if (l > r)
            return 0;
        int ln = Lg[r - l + 1], p1 = f[ln][l], p2 = f[ln][r - (1 << ln) + 1];
        if (ay[p1] > ay[p2])
            return p2;
        else
            return p1;
    }
} rq;
void dfs(int x, int fa)
{
    fth[x] = fa;
    dep[x] = dep[fa] + 1;
    in[x] = ++tot;
    ord[tot] = x;
    for (int i = fst[x]; i; i = nxt[i])
    {
        int y = to[i], z = wei[i];
        if (y == fa)
            continue;
        dis[y] = dis[x] + z;
        dfs(y, x);
        ord[++tot] = x;
    }
}
LL dist(int x, int y)
{
    if (in[x] > in[y])
        swap(x, y);
    return dis[x] + dis[y] - 2 * dis[ord[rq.ask(in[x], in[y])]];
}
struct chain
{
    int x, y;
    LL d;
    LL dit()
    {
        return d = dist(x, y);
    }
    friend chain operator+(const chain a, const int b)
    {
        int mx;
        chain c, d, e;
        c = d = e = a;
        c.y = b;
        d.x = b;
        mx = max(c.dit(), max(d.dit(), e.dit()));
        if (c.d == mx)
            return c;
        if (d.d == mx)
            return d;
        return e;
    }
} pre[N];
int main()
{
    cin >> n >> q;
    for (int i = 1; i <= n; i++)
    {
        scanf("%d", a + i);
        if (a[i] > n)
            continue;
        b[a[i]] = i;
    }
    for (int i = 0; i <= n; i++)
        if (!b[i])
        {
            up = i;
            break;
        }
    if (!up)
    {
        while (q--)
            puts("0");
        return 0;
    }
    for (int i = 1; i < n; i++)
    {
        int u, v, w;
        scanf("%d%d%d", &u, &v, &w);
        add(u, v, w), add(v, u, w);
    }
    tot = 0;
    dfs(1, 0);
    for (int i = 1; i <= tot; i++)
        stg[i] = dep[ord[i]];
    rq.build(stg, tot);
    pre[0].x = pre[0].y = b[0];
    pre[0].d = 0;
    for (int i = 1; i < up; i++)
        pre[i] = pre[i - 1] + b[i];
    while (q--)
    {
        int x, l = 0, r = up - 1, mid;
        LL y;
        scanf("%d%lld", &x, &y);
        while (l < r)
        {
            mid = l + r >> 1;
            if (max(dist(x, pre[mid].x), dist(x, pre[mid].y)) > y)
                r = mid;
            else
                l = mid + 1;
        }
        if (max(dist(x, pre[l].x), dist(x, pre[l].y)) <= y)
            l++;
        printf("%d\n", l);
    }
    return 0;
}