#include <bits/stdc++.h>
#pragma GCC optimize (3,"Ofast","inline")
using namespace std;
typedef long long ll;
typedef pair<int,int> pii;
const int MAXN=5e5+10;
const int mod=1e9+7;
const int K=20;
int F[K+1][MAXN];
vector<pii>e[MAXN];
pii a[MAXN];
int dfn[MAXN];
int tt=0;
inline int Min(int u,int v){return dfn[u]<dfn[v]?u:v;}
ll d[MAXN];
void dfs(int u,int fa)
{
    dfn[u]=++tt;
    F[0][dfn[u]]=fa;
    for(auto&[v,w]:e[u])if(v!=fa)d[v]=d[u]+w,dfs(v,u);
}
inline int LCA(int u,int v)
{
    if(u==v)return u;
    u=dfn[u],v=dfn[v];
    if(u>v)swap(u,v);
    int k=__lg(v-u);
    return Min(F[k][u+1],F[k][v-(1<<k)+1]);
}
inline ll dis(int u,int v){return d[u]+d[v]-2ll*d[LCA(u,v)];}
pii b[MAXN];
signed main() {
	
    ios::sync_with_stdio(0),cin.tie(0),cout.tie(0);
    int n,T;cin>>n>>T;
    for(int i=1;i<=n;i++)cin>>a[i].first,a[i].second=i;
    sort(a+1,a+n+1);
    for(int i=1,u,v,w;i<n;i++)cin>>u>>v>>w,e[u].emplace_back(v,w),e[v].emplace_back(u,w);
    dfs(1,0);
    for(int i=1;i<=K;i++)
        for(int j=1;j+(1<<i)-1<=n;j++)
            F[i][j]=Min(F[i-1][j],F[i-1][j+(1<<(i-1))]);
    int endd=n+1;
    for(int i=1;i<=n;i++)if(a[i].first!=i-1){endd=i;break;}
    b[0]={a[1].second,a[1].second};
    for(int i=1;i<endd;i++)
    {
        int u=a[i+1].second;
        b[i]=b[i-1];
        if(dis(u,b[i-1].first)>dis(b[i].first,b[i].second))b[i]={u,b[i-1].first};
        if(dis(u,b[i-1].second)>dis(b[i].first,b[i].second))b[i]={u,b[i-1].second};
    }
    //cerr<<b[1].first<<'\n';
    while(T--)
    {
        int u;ll k;cin>>u>>k;
        int l=0,r=endd-1,ans=-1;
        while(l<=r)
        {
            int mid=(l+r)>>1;
         //   cerr<<mid<<' '<<max(dis(b[mid].first,u),dis(b[mid].second,u))<<'\n';
            if(max(dis(b[mid].first,u),dis(b[mid].second,u))>k)r=mid-1;
            else l=mid+1,ans=mid;
        }
        cout<<ans+1<<'\n';
    }
    return 0;
}
/*
6 1
a?b??c
2 2 2
 */