#include<bits/stdc++.h>
using namespace std;
typedef long long ll;

#define N 500000

int i,j,k,n,m,t,dfn[N+50],it,pos[N+50];
vector<pair<int,int> > v[N+50];

ll dep[N+50];

struct SB{
	int i,j,k,n;
	int f[N+50][22],l2[N+50];
	int _get(int l,int r){
		return (dfn[l]<dfn[r]?l:r);
	}
	void init(int nn){
		n=nn;
		for(i=1;i<=20;i++)for(j=1;j+(1<<i)-1<=n;j++)f[j][i]=_get(f[j][i-1],f[j+(1<<(i-1))][i-1]);
	}
	int lca(int l,int r){
		if(l==r)return l;
		l=dfn[l]; r=dfn[r]; if(l>r)swap(l,r);
		l++; int k=l2[r-l+1];
		return _get(f[l][k],f[r-(1<<k)+1][k]);
	}
	ll dis(int x,int y){
		int z=lca(x,y);
		return dep[x]+dep[y]-2*dep[z];
	}
}sb;

void dfs0(int x,int fa){
	dfn[x]=++it; sb.f[it][0]=fa;
	for(auto [i,j]:v[x])if(i!=fa){
		dep[i]=dep[x]+j;
		dfs0(i,x);
	}
}

struct JB{
	int x,y; ll w;
}f[N+50];

JB hb(JB x,JB y){
	auto [x1,y1,w1]=x;
	auto [x2,y2,w2]=y;
	vector<int> v={x1,y1,x2,y2};
	int rx=0,ry=0,rw=-1,k;
	for(int i=0;i<4;i++)for(int j=i+1;j<4;j++){
		k=sb.dis(v[i],v[j]);
		if(k>rw){rw=k; rx=v[i]; ry=v[j];}
	}
	return {rx,ry,rw};
}

ll fuck(ll x,ll y){
	int res=0,l=1,r=m+1,md;
	ll t1;
	while(l<=r){
		md=(l+r)/2;
		t1=max(sb.dis(x,f[md-1].x),sb.dis(x,f[md-1].y));
		if(t1<=y){
			res=max(res,md); l=md+1;
		}
		else r=md-1;
	}
	return res;
}

int main(){
	for(i=2;i<=N;i++)sb.l2[i]=sb.l2[i/2]+1;
	ios::sync_with_stdio(0); cin.tie(0);
	cin>>n>>t;
	for(i=1;i<=n;i++){
		cin>>k;
		if(k<=n)pos[k]=i;
	}
	if(!pos[0]){
		while(t--)cout<<0<<'\n';
		return 0;
	}
	for(i=1;i<n;i++){
		int x,y,z;
		cin>>x>>y>>z;
		v[x].push_back({y,z});
		v[y].push_back({x,z});
	}
	dfs0(1,0);
	sb.init(n);
	//for(i=1;i<=n;i++)for(j=i+1;j<=n;j++){cout<<"NMSL "<<i<<' '<<j<<' '<<sb.dis(i,j)<<endl;}
	
	f[0]={pos[0],pos[0],0};
	for(i=1;i<=n;i++){
		if(!pos[i])break;
		m++;
		f[i]={pos[i],pos[i],0};
		f[i]=hb(f[i],f[i-1]);
	}
	while(t--){
		ll x,y;
		cin>>x>>y;
		cout<<fuck(x,y)<<'\n';
	}
}