#include <bits/stdc++.h>

typedef long long s64;

const int N = 500100;

int n, Q;
int a[N];

int id[N];
bool cmp(int x, int y) {
    return a[x] < a[y];
}

int tot, head[N], ver[N * 2], edge[N * 2], Next[N * 2];
void add_edge(int u, int v, int w) {
    ver[++ tot] = v;    edge[tot] = w;    Next[tot] = head[u];    head[u] = tot;
}

int dep[N];
s64 dist[N];

int Fir[N];
int eul_len, eul[N * 2];

void dfs(int u, int fu) {
    dep[u] = dep[fu] + 1;

    eul[++ eul_len] = u, Fir[u] = eul_len;

    for (int i = head[u]; i; i = Next[i]) {
        int v = ver[i], w = edge[i];
        if (v == fu) continue;

        dist[v] = dist[u] + w;
        dfs(v, u), eul[++ eul_len] = u;
    }
}

namespace eul_ST {
    int logx[N * 2];
    int f[20][N * 2];

    int great(int x, int y) {
        return dep[x] < dep[y] ? x : y;
    }

    void init() {
        logx[0] = -1;
        for (int i = 1; i <= eul_len; i ++) logx[i] = logx[i >> 1] + 1;

        for (int i = 1; i <= eul_len; i ++) f[0][i] = eul[i];
        for (int j = 1; j <= 19; j ++)
            for (int i = 1; i <= eul_len - (1 << j) + 1; i ++)
                f[j][i] = great(f[j - 1][i], f[j - 1][i + (1 << (j - 1))]);
    }

    int query(int l, int r) {
        int k = logx[r - l + 1];
        return great(f[k][l], f[k][r - (1 << k) + 1]);
    }
}

int lca(int x, int y) {
    int l = Fir[x], r = Fir[y]; if (l > r) std::swap(l, r);
    return eul_ST::query(l, r);
}

s64 calc(int x, int y) {
    return dist[x] + dist[y] - 2 * dist[lca(x, y)];
}

int px[N], qx[N];

int main() {
    scanf("%d%d", &n, &Q);

    for (int i = 1; i <= n; i ++)
        scanf("%d", &a[i]);

    for (int i = 1; i <= n; i ++)
        id[i] = i;
    std::sort(id + 1, id + 1 + n, cmp);

    for (int i = 1, u, v, w; i < n; i ++) {
        scanf("%d%d%d", &u, &v, &w);
        add_edge(u, v, w), add_edge(v, u, w);
    }

    dfs(1, 0);

    eul_ST::init();

    int p = 0;
    for (int i = 1; i <= n + 1; i ++)
        if (a[id[i]] != i - 1) {
            p = i - 2;
            break;
        }

    int P, Q; s64 max_dist = 0;
    px[0] = P = id[1], qx[0] = Q = id[1];
    for (int i = 1; i <= p; i ++) {
        int u = id[i + 1]; s64 tmp_dist;
        
        tmp_dist = calc(u, px[i - 1]);
        if (tmp_dist > max_dist) max_dist = tmp_dist, P = px[i - 1], Q = u;

        tmp_dist = calc(u, qx[i - 1]);
        if (tmp_dist > max_dist) max_dist = tmp_dist, P = u, Q = qx[i - 1];

        px[i] = P, qx[i] = Q;
    }

    while (Q --) {
        int x; s64 k;
        scanf("%d%lld", &x, &k);

        int l = 0, r = p + 1;
        while (l < r) {
            int mid = (l + r + 1) >> 1;
            if (calc(x, px[mid - 1]) <= k && calc(x, qx[mid - 1]) <= k) l = mid; else r = mid - 1;
        }

        printf("%d\n", l);
    }

    return 0;
}