#include<bits/stdc++.h>
using namespace std;
#define pb push_back
#define pii pair<int,int>
#define piii tuple<int,int,int>
#define mp make_pair
#define mt make_tuple
#define fi first
#define se second
#define deb(var) cerr<<#var<<'='<<(var)<<"; "
#define int long long
vector<pii> g[500010];
int n,q,a[500010],b[500010];
int dep[500010],dis[500010],anc[500010][20];
void dfs(int u,int fa){
	for(auto t:g[u]){
		int v,w;tie(v,w)=t;
		if(v==fa)continue;
		dep[v]=dep[u]+1,dis[v]=dis[u]+w;
		anc[v][0]=u;for(int i=1;i<20;i++)anc[v][i]=anc[anc[v][i-1]][i-1];dfs(v,u);
	}
} 
int lca(int u,int v){
	if(dep[u]<dep[v])swap(u,v);
	for(int i=19;~i;i--)
		if((dep[u]-dep[v])>>i&1)u=anc[u][i];
	if(u==v)return u;
	for(int i=19;~i;i--)
		if(anc[u][i]!=anc[v][i])u=anc[u][i],v=anc[v][i];return anc[u][0];
}
int dist(int u,int v){
	return dis[u]+dis[v]-2*dis[lca(u,v)];
}
pii dia[500010];
pii operator +(pii x,int c){
	int a,b;tie(a,b)=x;
	int t=max({dist(a,b),dist(a,c),dist(b,c)});
	if(dist(a,b)==t)return {a,b};if(dist(a,c)==t)return {a,c};return {b,c};
}
int chk(int u,pii d){
	int x,y;tie(x,y)=d;
	return max({dist(u,x),dist(u,y)});
}
void work(){
	cin>>n>>q;
	for(int i=1;i<=n;i++){
		cin>>a[i];
		if(a[i]<=n)b[a[i]]=i;
	}
	for(int i=1,u,v,w;i<n;i++)cin>>u>>v>>w,g[u].pb({v,w}),g[v].pb({u,w});dfs(1,0);
	
	int mex;
	for(int i=0;i<=n;i++){
		if(!b[i]){mex=i;break;}
		dia[i]=i?dia[i-1]+b[i]:mp(b[i],b[i]);
	}
	while(q--){
		int u,k;
		cin>>u>>k;
		int l=0,r=mex;
		while(l<r){
			int mid=(l+r)>>1;
			if(chk(u,dia[mid])>k)r=mid;else l=mid+1;
		}cout<<l<<'\n';
	}
}
signed main(){
	ios::sync_with_stdio(0),
	cin.tie(0),cout.tie(0);
	int T=1;while(T--)work();return 0;
}