#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];
// vector<pair<int, int>>
int tim; 
pair<int, int> dfn[N];
pair<int, int> minn[22][N];
int st[N], ed[N];
int pos[N];
int w[N];
int maxn;
int ans[N];
int lg[N];
Que q[N], tmp[N];

void dfs(int u, int _fa) {
    dep[u] = dep[_fa] + 1;
    dfn[++tim] = make_pair(dep[u], u);
    st[u] = tim;
    for (auto it : path[u]) {
        int v = it.first, w = it.second;
        if (v == _fa) continue;
        dis[v] = dis[u] + w;
        dfs(v, u);
        dfn[++tim] = make_pair(dep[u], u);
        ed[u] = tim;
    }
}

int lca(int x, int y) {
    if (st[x] > st[y]) swap(x, y);
    int l = st[x], r = st[y];
    int k = lg[r - l + 1];
    return min(minn[k][l], minn[k][r - (1 << k) + 1]).second;

}

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

Line merge(Line a, int b) {
    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() {
    lg[1] = 0;
    for (int i = 2; i <= 1000000; ++i) {
        lg[i] = lg[i >> 1] + 1;
    }
    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);
    }
    dfs(1, 0);
    // for (int k = )
    for (int i = 1; i <= tim; ++i) minn[0][i] = dfn[i];
    for (int k = 1; k <= 20; ++k) {
        for (int i = 1; i <= tim - (1 << k) + 1; ++i) {
            minn[k][i] = min(minn[k - 1][i], minn[k - 1][i + (1 << (k - 1))]);
        }
    }
    // for (int i = 1; i <= n; ++i) {
    //     for (int j = 1; j <= n; ++j) {
    //         cerr << lca(i, j) << ' ' ;
    //     }
    //     cerr << '\n';
    // }
    stk[0] = (Line){pos[0], pos[0], 0};
    for (int i = 1; i <= maxn - 1; ++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);
    }
    return 0;
}