// sis puella oier
#include <bits/stdc++.h>
using namespace std;
#define int long long
typedef long long ll;
ll read(){
    ll xx = 0, f = 1; char ch = getchar();
    for (;!isdigit(ch); ch = getchar())
        f = (ch == '-' ? -1 : 1);
    for (; isdigit(ch); ch = getchar())
        xx = (xx << 3) + (xx << 1) + ch - '0';
    return xx * f;
}
const int N = 500100;
int n, q;
struct edge{
    int v, w;
};
vector <edge> e[N];
int a[N], dep[N], fa[19][N];
void dfs(int x, int fath){
    fa[0][x] = fath; for (int i = 1; i <= 18; ++i)fa[i][x] = fa[i - 1][fa[i - 1][x]];
    for (edge v : e[x])if (v.v != fath)dep[v.v] = dep[x] + v.w, dfs(v.v, x);
}
int lca(int x, int y){
    if (dep[x] < dep[y])swap(x, y);
    for (int i = 18; i >= 0; --i)if (dep[fa[i][x]] >= dep[y])x = fa[i][x];
    if (x == y)return x;
    for (int i = 18; i >= 0; --i)if (fa[i][x] != fa[i][y])x = fa[i][x], y = fa[i][y];
    return fa[0][x];
}
int dis(int x, int y){
    return dep[x] + dep[y] - 2 * dep[lca(x, y)];
}
edge qu[N];
int id[N], idl[N], idr[N], ans[N];
int dd[2][N];
void solve(int l, int r, int nl, int nr){
    if (nl > nr)return ;
    // cout<<l<<" "<<r<<endl;
    if (l == r){
        for (int i = nl; i <= nr; ++i)ans[id[i]] = l;
        return ;
    }
    int mid = (l + r) >> 1, cntl = 0, cntr = 0;
    // cout<<mid<<" :: "<<dd[0][mid]<<" "<<dd[1][mid]<<" : "<<qu[id[nl]].v<<endl;
    // cout<<max(dis(dd[0][mid], qu[id[nl]].v), dis(dd[1][mid], qu[id[nl]].v))<<endl;
    for (int i = nl; i <= nr; ++i)if (max(dis(dd[0][mid], qu[id[i]].v), dis(dd[1][mid], qu[id[i]].v)) > qu[id[i]].w)
        idl[++cntl] = id[i];
    else idr[++cntr] = id[i];
    for (int i = 1; i <= cntl; ++i)id[nl + i - 1] = idl[i];
    for (int i = 1; i <= cntr; ++i)id[nl + cntl + i - 1] = idr[i];
    solve(l, mid, nl, nl + cntl - 1), solve(mid + 1, r, nl + cntl, nr);
}
int vis[N];
signed main(){
    n = read(), q = read();
    for (int i = 1; i <= n; ++i){
        a[i] = read(); if (a[i] < N)vis[a[i]] = i;
    }
    // for (int i = 0; i <= n; ++i)cout<<vis[i]<<" ";cout<<endl;
    int mx = 0; while(vis[mx])++mx;
    for (int i = 1, u, v, w; i < n; ++i)u = read(), v = read(), w = read(),
    e[u].push_back(edge{v, w}), e[v].push_back(edge{u, w});
    dep[1] = 0, dfs(1, 0);
    dd[0][0] = vis[0], dd[1][0] = vis[0];
    for (int i = 1; i < mx; ++i){
        int xx = dis(vis[i], dd[0][i - 1]), yy = dis(vis[i], dd[1][i - 1]),
        zz = dis(dd[0][i - 1], dd[1][i - 1]);
        if (xx >= yy && xx >= zz)dd[0][i] = vis[i], dd[1][i] = dd[0][i - 1];
        if (yy >= xx && yy >= zz)dd[0][i] = vis[i], dd[1][i] = dd[1][i - 1];
        if (zz >= xx && zz >= yy)dd[0][i] = dd[0][i - 1], dd[1][i] = dd[1][i - 1];
    }
    // for (int i = 0; i < mx; ++i)cout<<dd[0][i]<<" "<<dd[1][i]<<endl; cout<<endl;
    for (int i = 1; i <= q; ++i)qu[i].v = read(), qu[i].w = read(), id[i] = i;
    solve(0, mx, 1, q);
    for (int i = 1; i <= q; ++i)printf("%lld\n", ans[i]);
    return 0;
}