#include<bits/stdc++.h>
#define MAX 500005
using namespace std;
#define ll long long
int n,Que;

#define pil pair<int,ll>
#define fi first
#define se second
vector<pil> e[MAX],E[MAX];

//lca预处理
int dep[MAX];ll d[MAX];
int bg[MAX],ceul;
int ST[MAX<<1][22];
void dfs(int x,int f){
    ST[++ceul][0]=x;
    bg[x]=ceul;
    for(auto o:e[x]){
        int y=o.fi;ll w=o.se;
        if(y==f) continue;
        dep[y]=dep[x]+1;
        d[y]=d[x]+w;
        dfs(y,x);
        ST[++ceul][0]=x;
    }
}
int MIN(int a,int b){
    if(dep[a]<dep[b]) return a;
    return b;
}
int lg2[MAX<<1];
int lca(int a,int b){
    a=bg[a],b=bg[b];
    if(a>b) swap(a,b);
    int k=lg2[b-a+1];
    return MIN(ST[a][k],ST[b-(1<<k)+1][k]);
}
ll dis(int x,int y){
    int lc=lca(x,y);
    return d[x]+d[y]-2*d[lc];
}
void init(){
    dfs(1,0);
    for(int i=2;i<=ceul;i++)
        lg2[i]=lg2[i>>1]+1;
    for(int j=1;(1<<j)<=ceul;j++)
        for(int i=1;i+(1<<j)-1<=ceul;i++)
            ST[i][j]=min(ST[i][j-1],ST[i+(1<<(j-1))][j-1]);
}

int W[MAX],pos[MAX],mx;
#define pii pair<int,int>
pii dia[MAX];
pii Max(pii a,pii b){
    ll l1=dis(a.fi,a.se),l2=dis(b.fi,b.se);
    if(l1>=l2) return a;
    return b;
}
void sol(){
    cin>>n>>Que;
    for(int i=1;i<=n;i++){
        W[i]=i;
        cin>>W[i];
        if(W[i]<=n) pos[W[i]]=i;
    }
    while(pos[mx]) mx++;
    for(int i=1,x,y;i<n;i++){
        ll w;
        cin>>x>>y>>w;
        e[x].push_back({y,w});
        e[y].push_back({x,w});
    }
    init();
    dia[0]={pos[0],pos[0]};
    for(int i=1;i<mx;i++){
        int x=dia[i-1].fi,y=dia[i-1].se;
        dia[i]=Max(pii{x,y},Max(pii{x,pos[i]},pii{y,pos[i]}));
    }
    for(int i=1;i<=Que;i++){
        int x;ll k;cin>>x>>k;
        int l=0,r=mx-1,rt=-1;
        while(l<=r){
            int mid=(l+r)>>1;
            int a=dia[mid].fi,b=dia[mid].se;
            if(dis(a,x)<=k&&dis(b,x)<=k){
                rt=mid;l=mid+1;
            }else r=mid-1;
        }
        cout<<rt+1<<"\n";
    }
}
int main(){
    srand(time(0));
    ios::sync_with_stdio(0);
    cin.tie(0);
    int t=1;
    while(t--) sol();
}
// g++ b.cpp -Wl,--stack=10000000 -o b && b < in.txt > out.txt