#pragma GCC optimize(2)
#include<bits/stdc++.h>
using namespace std;
const int MAX=5e5+5;
long long g[MAX][3];
int n,tot,lst;
struct edge{
	int nxt,to,w;
};
edge e[MAX*2];
int h[MAX],a[MAX],b[MAX],dep[MAX],f[MAX][21],q;
long long dis[MAX];

void addedge(int u,int v,int w){
	e[++tot].to=v;
	e[tot].nxt=h[u];
	e[tot].w=w;
	h[u]=tot;
}
void pre(int u,int fa){
	dep[u]=dep[fa]+1;
	for(int i=0;i<=19;++i)
		f[u][i+1]=f[f[u][i]][i];
	for(int i=h[u];i;i=e[i].nxt){
		int v=e[i].to;
		if(v==fa)
			continue;
		dis[v]=dis[u]+e[i].w;
		f[v][0]=u;
		pre(v,u);
	}
}
long long dist(int x,int y){
	if(x==y)
		return 0;
	int u=x,v=y;
	if(dep[x]<dep[y])
		swap(x,y);
	for(int i=20;i>=0;--i){
		if(dep[f[x][i]]>=dep[y])
			x=f[x][i];
		if(x==y)
			return dis[u]+dis[v]-2*dis[x];
	}
	for(int i=20;i>=0;--i){
		if(f[x][i]!=f[y][i]){
			x=f[x][i];
			y=f[y][i];
		}
	}
	int lca=f[x][0];
	return dis[u]+dis[v]-2*dis[lca];
} 
// 快读 
int read(){
	int x = 0;
	char c = getchar();
	while(c < '0' || c > '9'){
		c = getchar();
	}
	while(c >= '0' && c <= '9'){
		x = x*10+c-'0';
		c = getchar();
	}
	return x;
}
long long readL(){
	long long x = 0;
	char c = getchar();
	while(c < '0' || c > '9'){
		c = getchar();
	}
	while(c >= '0' && c <= '9'){
		x = x*10+c-'0';
		c = getchar();
	}
	return x;
}
int main(){
	n=read(),q=read();
	for(int i=1;i<=n;++i){
		a[i]=read();
		if(a[i]<=n)
			b[a[i]]=i;
	}
	for(int i=1;i<=n-1;++i){
		int u=read(),v=read(),w=read();
		addedge(u,v,w);
		addedge(v,u,w);
	}
	
	for(int i=0;i<=n;++i){
		if(!b[i]){
			lst=i-1;
			break;
		}
	}

	pre(1,0);
	 
	if(lst>=0)
		g[0][0]=g[0][1]=b[0];
	for(int i=1;i<=lst;++i){
		int d0=dist(b[i],g[i-1][0]);
		int d1=dist(b[i],g[i-1][1]);
	//	cout<<b[i]<<" "<<g[i][0]<<" "<<g[i][1]<<"^"<<i<<" "<<d0<<" "<<d1<<endl;
		g[i][0]=g[i-1][0],g[i][1]=g[i-1][1],g[i][2]=g[i-1][2];
		if(d1>=d0&&d1>g[i-1][2]){
			g[i][0]=b[i];
			g[i][2]=d1;
		}
		else
			if(d0>=d1&&d0>g[i-1][2]){
				g[i][1]=b[i];
				g[i][2]=d0;
			}
	//	cout<<"&"<<i<<" "<<g[i][0]<<" "<<g[i][1]<<endl;
	}
//	cout<<lst<<" "<<endl; 
	while(q--){
		int u=read();
		long long d=readL();
		int l=0,r=lst,res=-1;
		while(l<=r){
			int mid=l+r>>1;
		//	cout<<mid<<endl;
			if(dist(u,g[mid][0])<=d&&dist(u,g[mid][1])<=d){
				res=mid;
				l=mid+1;
			}
			else
				r=mid-1;
		}
		res++;
		printf("%d\n",res);
	}	
}