// 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; ll w;
};
vector <edge> e[N];
int a[N];
ll dis[N];
int st[20][N << 1], lg[N << 1], fir[N], dfn;
void dfs(int x, int fath){
    st[0][++dfn] = x, fir[x] = dfn;
    for (edge v : e[x])
        if (v.v != fath)dis[v.v] = dis[x] + v.w, dfs(v.v, x),
        st[0][++dfn] = x;
}
int query(int l, int r){
    int len = lg[r - l + 1];
    return min(st[len][l], st[len][r - (1 << len) + 1]);
}
int lca(int x, int y){
    x = fir[x], y = fir[y]; if (x > y)swap(x, y);
    return query(x, y);
}
ll Dis(int x, int y){
    return dis[x] + dis[y] - 2ll * dis[lca(x, y)];
}
int dd[2][N];
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;
    }
    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});
    dis[1] = 0, dfs(1, 0);
    lg[0] = -1; for (int i = 1; i <= dfn; ++i)lg[i] = lg[i >> 1] + 1;
    for (int i = 1; i < 20; ++i)
        for (int j = 1; j + (1 << i) - 1 <= dfn; ++j)
            st[i][j] = min(st[i - 1][j], st[i - 1][j + (1 << (i - 1))]);
    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;
    while(q--){
        int x = read(); ll w = read();
        int l = 0, r = mx, mid;
        while(l < r){
            mid = (l + r) >> 1;
            if (max(Dis(dd[0][mid], x), Dis(dd[1][mid], x)) > w)r = mid;
            else l = mid + 1;
        }
        printf("%lld\n", l);
    }
    return 0;
}