/*
  author: honglan0301
  Sexy_goodier _ xiaoqing
 */
#include <iostream>
#include <cstring>
#include <algorithm>
#include <cstdio>
#include <cctype>
#include <queue>
#include <map>
#include <unordered_map>
#include <cstdlib>
#include <ctime>
#include <vector>
#include <cmath>
#include <random>
#include <set>
#include <bitset>
#include <assert.h>
using namespace std;

//namespace Fread{const int SIZE=1<<20;char buf[SIZE],*S,*T;inline char getchar(){if(S==T){T=(S=buf)+fread(buf,1,SIZE,stdin);if(S==T)return'\n';}return*S++;}}using namespace Fread;namespace Fwrite{const int SIZE=1<<20;char buf[SIZE],*S=buf,*T=buf+SIZE;inline void flush(){fwrite(buf,1,S-buf,stdout);S=buf;}inline void putchar(char c){*S++=c;if(S==T)flush();}struct NTR{~NTR(){flush();}}ztr;}using namespace Fwrite;
//#define getchar Fread::getchar
//#define putchar Fwrite::putchar

namespace Fastio{struct Reader{template<typename T>Reader&operator>>(T&x){x=0;short f=1;char c=getchar();while(c<'0'||c>'9'){if(c=='-')f*=-1;c=getchar();}while(c>='0'&&c<='9')x=(x<<3)+(x<<1)+(c^48),c=getchar();x*=f;return*this;}Reader&operator>>(double&x){x=0;double t=0;short f=1,s=0;char c=getchar();while((c<'0'||c>'9')&&c!='.'){if(c=='-')f*=-1;c=getchar();}while(c>='0'&&c<='9'&&c!='.')x=x*10+(c^48),c=getchar();if(c=='.')c=getchar();else{x*=f;return*this;}while(c>='0'&&c<='9')t=t*10+(c^48),s++,c=getchar();while(s--)t/=10.0;x=(x+t)*f;return*this;}Reader&operator>>(long double&x){x=0;long double t=0;short f=1,s=0;char c=getchar();while((c<'0'||c>'9')&&c!='.'){if(c=='-')f*=-1;c=getchar();}while(c>='0'&&c<='9'&&c!='.')x=x*10+(c^48),c=getchar();if(c=='.')c=getchar();else{x*=f;return*this;}while(c>='0'&&c<='9')t=t*10+(c^48),s++,c=getchar();while(s--)t/=10.0;x=(x+t)*f;return*this;}Reader&operator>>(__float128&x){x=0;__float128 t=0;short f=1,s=0;char c=getchar();while((c<'0'||c>'9')&&c!='.'){if(c=='-')f*=-1;c=getchar();}while(c>='0'&&c<='9'&&c!='.')x=x*10+(c^48),c=getchar();if(c=='.')c=getchar();else{x*=f;return*this;}while(c>='0'&&c<='9')t=t*10+(c^48),s++,c=getchar();while(s--)t/=10.0;x=(x+t)*f;return*this;}Reader&operator>>(char&c){c=getchar();while(c==' '||c=='\n'||c=='\r')c=getchar();return*this;}Reader&operator>>(char*str){int len=0;char c=getchar();while(c==' '||c=='\n'||c=='\r')c=getchar();while(c!=' '&&c!='\n'&&c!='\r')str[len++]=c,c=getchar();str[len]='\0';return*this;}Reader&operator>>(string&str){str.clear();char c=getchar();while(c==' '||c=='\n'||c=='\r')c=getchar();while(c!=' '&&c!='\n'&&c!='\r')str.push_back(c),c=getchar();return*this;}Reader(){}}cin;const char endl='\n';struct Writer{const int Setprecision=6;typedef int mxdouble;template<typename T>Writer&operator<<(T x){if(x==0){putchar('0');return*this;}if(x<0)putchar('-'),x=-x;static short sta[40];short top=0;while(x>0)sta[++top]=x%10,x/=10;while(top>0)putchar(sta[top]+'0'),top--;return*this;}Writer&operator<<(double x){if(x<0)putchar('-'),x=-x;mxdouble _=x;x-=(double)_;static short sta[40];short top=0;while(_>0)sta[++top]=_%10,_/=10;if(top==0)putchar('0');while(top>0)putchar(sta[top]+'0'),top--;putchar('.');for(int i=0;i<Setprecision;i++)x*=10;_=x;while(_>0)sta[++top]=_%10,_/=10;for(int i=0;i<Setprecision-top;i++)putchar('0');while(top>0)putchar(sta[top]+'0'),top--;return*this;}Writer&operator<<(long double x){if(x<0)putchar('-'),x=-x;mxdouble _=x;x-=(long double)_;static short sta[40];short top=0;while(_>0)sta[++top]=_%10,_/=10;if(top==0)putchar('0');while(top>0)putchar(sta[top]+'0'),top--;putchar('.');for(int i=0;i<Setprecision;i++)x*=10;_=x;while(_>0)sta[++top]=_%10,_/=10;for(int i=0;i<Setprecision-top;i++)putchar('0');while(top>0)putchar(sta[top]+'0'),top--;return*this;}Writer&operator<<(__float128 x){if(x<0)putchar('-'),x=-x;mxdouble _=x;x-=(__float128)_;static short sta[40];short top=0;while(_>0)sta[++top]=_%10,_/=10;if(top==0)putchar('0');while(top>0)putchar(sta[top]+'0'),top--;putchar('.');for(int i=0;i<Setprecision;i++)x*=10;_=x;while(_>0)sta[++top]=_%10,_/=10;for(int i=0;i<Setprecision-top;i++)putchar('0');while(top>0)putchar(sta[top]+'0'),top--;return*this;}Writer&operator<<(char c){putchar(c);return*this;}Writer&operator<<(char*str){int cur=0;while(str[cur])putchar(str[cur++]);return*this;}Writer&operator<<(const char*str){int cur=0;while(str[cur])putchar(str[cur++]);return*this;}Writer&operator<<(string str){int st=0,ed=str.size();while(st<ed)putchar(str[st++]);return*this;}Writer(){}}cout;}using namespace Fastio;
#define cin Fastio::cin
#define cout Fastio::cout
#define endl Fastio::endl//;fflush(stdout)
#define mp make_pair
#define pb push_back
#define fi first
#define se second
#define int long long
#define ull unsigned long long
#define mod 1000000007
mt19937 rnd(time(0));
mt19937_64 rndl(time(0));

int n,q,a[500005],wz[500005],ans[500005],u,v,w,dep[500005],qu[500005],qv[500005];
int dfn[500005],cntd,st[21][500005],lg[500005];
vector <pair<int,int>> e[500005];

void dfs1(int x,int fat)
{
	st[0][dfn[x]=++cntd]=fat;
	for(auto i:e[x]) {if(i.fi==fat) continue; dep[i.fi]=dep[x]+i.se; dfs1(i.fi,x);}
}
int getm(int x,int y) {return dfn[x]<dfn[y]?x:y;}
bool cmp(int x,int y) {return dfn[x]<dfn[y];}
void init()
{
	for(int i=1;(1<<i)<=n;i++) for(int j=(1<<i);j<=(1<<(i+1))-1;j++) lg[j]=i;
	for(int i=1;i<=lg[n];i++) for(int j=1;j+(1<<i)-1<=n;j++) st[i][j]=getm(st[i-1][j],st[i-1][j+(1<<i-1)]);
}
int lca(int x,int y)
{
	if(x==y) return x; if((x=dfn[x])>(y=dfn[y])) swap(x,y);
	int dd=lg[y-x++]; return getm(st[dd][x],st[dd][y-(1<<dd)+1]);
}
int dis(int x,int y) {return dep[x]+dep[y]-2*dep[lca(x,y)];}

int nd[1000005],cntb,gj[500005],dp[500005],stk[500005],top;

struct dat
{
	int u,v,d;
	friend dat operator+(dat x,dat y)
	{
		dat z; z=x; if(y.d>x.d) z=y; int dd;
		dd=dis(x.u,y.u); if(dd>z.d) z={x.u,y.u,dd}; 
		dd=dis(x.u,y.v); if(dd>z.d) z={x.u,y.v,dd}; 
		dd=dis(x.v,y.u); if(dd>z.d) z={x.v,y.u,dd}; 
		dd=dis(x.v,y.v); if(dd>z.d) z={x.v,y.v,dd};
		return z; 
	}
};

void solve(int l,int r,vector <int> nq)
{
	vector <int> nl,nr; int mid=(l+r)>>1;
	int flag=1; for(int i=l;i<=mid;i++) if(!wz[i]) flag=0;
	cntb=0; for(auto i:nq) nd[++cntb]=qu[i]; 
	for(int i=l;i<=mid;i++) if(wz[i]) nd[++cntb]=wz[i]; nd[++cntb]=1;
	sort(nd+1,nd+cntb+1,cmp); cntb=unique(nd+1,nd+cntb+1)-nd-1;
	for(int i=1;i<=cntb;i++) dp[nd[i]]=0;
	int nf=0; dat nzj;
	for(int i=l;i<=mid;i++)
	{
		if(!wz[i]) continue;
		if(!nf) nf=1,nzj={wz[i],wz[i],0};
		else nzj=nzj+(dat){wz[i],wz[i],0};
	}
	if(!nf) nzj=(dat){1,1,0};
	for(auto i:nq)
	{
		//cout<<i<<" "<<qu[i]<<" "<<dp[qu[i]]<<endl;
		dp[qu[i]]=max(dis(qu[i],nzj.u),dis(qu[i],nzj.v));
		if(flag&&dp[qu[i]]<=qv[i]) ans[i]=mid,nr.pb(i); else nl.pb(i);
	}
	if(l==r) return; solve(l,mid,nl); solve(mid+1,r,nr);
}

signed main()
{
	cin>>n>>q;
	for(int i=1;i<=n;i++) cin>>a[i];
	for(int i=1;i<=n;i++) if(a[i]<=n) wz[a[i]]=i;
	for(int i=1;i<=n-1;i++) cin>>u>>v>>w,e[u].pb(mp(v,w)),e[v].pb(mp(u,w));
	dfs1(1,1); init();
	vector <int> nq;
	for(int i=1;i<=q;i++) cin>>qu[i]>>qv[i],nq.pb(i),ans[i]=-1;
	solve(0,n-1,nq);
	for(int i=1;i<=q;i++) cout<<ans[i]+1<<endl;
}//