#include<bits/stdc++.h>
#define rep(i,j,k) for(int i=j;i<=k;i++)
#define repp(i,j,k) for(int i=j;i>=k;i--)
#define ls(x) (x<<1)
#define rs(x) ((x<<1)|1)
#define mp make_pair
#define sec second
#define fir first
#define pii pair<int,int>
#define lowbit(i) i&-i
#define int long long
using namespace std;
typedef long long ll;
const int N=5e5+5,M=1e6+5,S=(1<<20)+5,inf=2e9+7,mo=998244853,base=620071201;
void read(int &p){
	int x=0,w=1;
	char ch=0;
	while(!isdigit(ch)){
		if(ch=='-')w=-1;
		ch=getchar();
	}
	while(isdigit(ch)){
		x=(x<<1)+(x<<3)+ch-'0';
		ch=getchar();
	}
	p=x*w;
}
int n,q;
vector<pii>e[N];
pii a[N];
struct dir{
    int x,y,len;
}d[N];
int eular[N*2],cnte,firp[N],dis[N];
struct ST_form{
    int st[N*2][22],lg[N*2];
    void init(){
        rep(i,2,cnte)
            lg[i]=lg[i/2]+1;
    }
    void build(){
        init();
        rep(i,1,cnte)
            st[i][0]=eular[i];
        rep(j,1,20){
            rep(i,1,cnte){
                st[i][j]=st[i][j-1];
                if(i+(1<<(j-1))<=cnte)st[i][j]=min(st[i][j],st[i+(1<<(j-1))][j-1]);
            }
        }
    }
    int query(int x,int y){
        if(x>y)swap(x,y);
        int len=(y-x+1);
        return min(st[x][lg[len]],st[y-(1<<lg[len])+1][lg[len]]);
    }
}ST;
void dfs(int x,int f){
    eular[++cnte]=x,firp[x]=cnte;
    for(auto j:e[x]){
        if(j.fir==f)continue;
        dis[j.fir]=dis[x]+j.sec;
        dfs(j.fir,x);
        eular[++cnte]=x;
    }
}
int lca(int x,int y){
    return ST.query(firp[x],firp[y]);
}
int getdis(int x,int y){
    return dis[x]+dis[y]-2ll*dis[lca(x,y)];
}
int upp=0;
bool check(int val,int x,int k){
    int dx=d[val].x,dy=d[val].y;
    if(getdis(x,dx)>k||getdis(x,dy)>k)return 1;
    return 0;
}
signed main(){
    read(n),read(q);
    rep(i,1,n)
        read(a[i].fir),a[i].sec=i;
    sort(a+1,a+n+1);
    rep(i,1,n){
        if(a[i].fir==i-1)upp=i;
        else break;
    }
    rep(i,1,n-1){
        int x,y,v;
        read(x),read(y),read(v);
        e[x].push_back(mp(y,v)),e[y].push_back(mp(x,v));
    }
    dfs(1,0);
    ST.build();
    d[1]=(dir){a[1].sec,a[1].sec,0};
    rep(i,2,n){
        int x=d[i-1].x,y=d[i-1].y,l=d[i-1].len;
        d[i]=d[i-1];
        int v1=getdis(x,a[i].sec),v2=getdis(y,a[i].sec);
        if(v1>v2&&v1>l)d[i]=(dir){x,a[i].sec,v1};
        else if(v2>=v1&&v2>l)d[i]=(dir){y,a[i].sec,v2};
    }
    while(q--){
        int x,k;
        read(x),read(k);
        int le=1,ri=upp,ans=upp;
        while(le<=ri){
            int mid=(le+ri)>>1;
            if(check(mid,x,k))ans=mid-1,ri=mid-1;
            else le=mid+1;
        }
        printf("%lld\n",ans);
    }
    return 0;
}