#include <bits/stdc++.h>

template <class T>
inline void read(T &x) {
	static char s;
	static bool opt;
	while (s = getchar(), (s < '0' || s > '9') && s != '-');
	x = (opt = s == '-') ? 0 : s - '0';
	while (s = getchar(), s >= '0' && s <= '9') x = x * 10 + s - '0';
	if (opt) x = ~x + 1;
}

typedef long long s64;

const int N = 500100;

int n, Q;
int a[N], 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 Fa[N];
int anc[19][N];
int dep[N];
s64 dist[N];

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

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

        Fa[v] = u;
        dist[v] = dist[u] + w;

        dfs(v);
    }
}

int lca(int x, int y) {
    if (dep[x] > dep[y]) std::swap(x, y);
    for (int i = 18; i >= 0; i --)
        if (dep[x] <= dep[y] - (1 << i)) y = anc[i][y];
    if (x == y) return x;
    for (int i = 18; i >= 0; i --)
        if (anc[i][x] ^ anc[i][y]) x = anc[i][x], y = anc[i][y];
    return anc[0][x];
}

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

int px[N], qx[N];

int main() {
    read(n), read(Q);

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

    for (int i = 1, x, y, z; i < n; i ++) {
        read(x), read(y), read(z);
        add_edge(x, y, z), add_edge(y, x, z);
    }

    dfs(1);

    for (int i = 1; i <= n; i ++) anc[0][i] = Fa[i];
    for (int j = 1; j <= 18; j ++)
        for (int i = 1; i <= n; i ++) anc[j][i] = anc[j - 1][anc[j - 1][i]];

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

    int pX = px[1] = id[1], qX = qx[1] = id[1];
    s64 dis = 0;
    for (int i = 2; i <= p; i ++) {
        int u = id[i]; s64 tmpP, tmpQ;

        tmpP = calc(u, pX);
        if (tmpP > dis) dis = tmpP, pX = px[i - 1], qX = u;

        tmpQ = calc(u, qX);
        if (tmpQ > dis) dis = tmpQ, pX = u, qX = qx[i - 1];

        px[i] = pX, qx[i] = qX;
    }

    while (Q --) {
        int x; s64 k;
        read(x), read(k);

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

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

    return 0;
}