#include<bits/stdc++.h>
#define vectorwyx maze
namespace vectorwyx{
#define pii pair<int,int>
#define fi first
#define se second
#define pb push_back
#define eb emplace_back
#define mk make_pair
#define sml(x,y) (x=min(x,y))
#define big(x,y) (x=max(x,y))
#define ll long long
#define uint unsigned
#define ull unsigned long long
#define umap unordered_map
#define db double
#define fo(i,x,y) for(int i=(x);i<=(y);++i)
#define go(i,x,y) for(int i=(x);i>=(y);--i)
#define ptc putchar
#define gtc getchar
#define emp emplace
#define re return
#define co continue
#define brk break
#define HH (ptc('\n'))
#define bctz __builtin_ctz
#define bclz __builtin_clz
#define bppc __builtin_popcount
using namespace std;
ll seed=chrono::system_clock::now().time_since_epoch().count();
mt19937 rnd(seed);
inline int rm(int x,int y){return (int)(rnd()%(y-x+1ll)+x);}
inline int read(){signed ch=getchar();int x=0,f=1;while(!isdigit(ch)){if(ch==(int)('-'))f=-1;ch=getchar();}while(isdigit(ch)){x=(x<<1)+(x<<3)+(ch^48);ch=getchar();}return x*f;}
inline ll llread(){signed ch=getchar();ll x=0,f=1;while(!isdigit(ch)){if(ch==(int)('-'))f=-1;ch=getchar();}while(isdigit(ch)){x=(x<<1)+(x<<3)+(ch^48);ch=getchar();}return x*f;}
template<typename T> void out(T *a,int l,int r){fo(i,l,r) cout<<*(a+i)<<' ';puts("");}

const int N=1e6+5;
int w[N],mp[N],n,q;
vector<pii> e[N];

void add(int x,int y,int v){
    e[x].eb(y,v);
    e[y].eb(x,v);
}

namespace Tree{
ll dis[N];
int dfn[N],ti,lg[N],dep[N],fa[N];
pii st[21][N];
void init(){
    fo(i,2,n) lg[i]=lg[i>>1]+1;
    fo(i,1,lg[n])
        fo(j,1,n) st[i][j]=min(st[i-1][j],st[i-1][min(n,j+(1<<(i-1)))]);
}
int rmq(int l,int r){
    int w=lg[r-l+1];
    re min(st[w][l],st[w][r-(1<<w)+1]).se;
}
int lca(int x,int y){
    if(x==y) re x;
    if(dfn[x]>dfn[y]) swap(x,y);
    re fa[rmq(dfn[x]+1,dfn[y])];
}
ll get_dis(int x,int y){re dis[x]+dis[y]-2*dis[lca(x,y)];}
void dfs(int x){
    dfn[x]=++ti;dep[x]=dep[fa[x]]+1;
    st[0][ti]=mk(dep[x],x);
    for(auto i:e[x]) if(i.fi!=fa[x]){
        fa[i.fi]=x,dis[i.fi]=dis[x]+i.se;
        dfs(i.fi);
    }
    if(x==1) init();
}
}
using Tree::get_dis;

pii dia[N];ll len[N];

signed main(){
    cin>>n>>q;
    fo(i,1,n) w[i]=read();
    fo(i,2,n){
        int x=read(),y=read();
        add(x,y,read());
    }
    Tree::dfs(1);
    fo(i,1,n) if(w[i]<n) mp[w[i]]=i;
    if(!mp[0]){
        while(q--) puts("0");
        re 0;
    }
    dia[0]=mk(mp[0],mp[0]);
    int lim=n;
    fo(i,1,n-1){
        int x=mp[i];
        if(!x){lim=i;break;}
        ll v=get_dis(x,dia[i-1].fi);
        if(v>len[i-1]){len[i]=v,dia[i]=mk(dia[i-1].fi,x);}
        v=get_dis(x,dia[i-1].se);
        if(v>len[i-1]){len[i]=v,dia[i]=mk(dia[i-1].se,x);}
        if(len[i]) co;
        len[i]=len[i-1],dia[i]=dia[i-1];
    }
    while(q--){
        int x=read();ll k=llread();
        int l=0,r=lim-1,ans=lim;
        while(l<=r){
            int mid=(l+r)>>1;
            ll v=max(get_dis(x,dia[mid].fi),get_dis(x,dia[mid].se));
            if(v>k) ans=mid,r=mid-1;
            else l=mid+1;
        }
        cout<<ans<<'\n';
    }
    return 0;
}
}
/*
-------------------------------------------------
*/










signed main(){re vectorwyx::main();}