// author:  jieda
// file:	cpp
//#pragma GCC optimize("O3")
#include<bits/stdc++.h>
using namespace std;
# define fi first
# define se second
# define all(x) x.begin(),x.end()
# define stst stringstream
# define pb push_back
# define pf push_front
# define pp push
# define lowbit(x) (x)&(-x)
# define fa(i,op,n) for (ll i = op; i <= n; i++)
# define fb(j,op,n) for (ll j = op; j >= n; j--)
# define fg(i,op,n) for (ll i = op; i != n; i = ne[i])
int dx[4] = {-1,0,1,0},dy[4] = {0,1,0,-1};
typedef unsigned long long  ull;
typedef long long ll;
typedef pair<ll,ll> Pll;
typedef pair<int,int> PII;
typedef pair<double,double> PDD;
const ll N = 1e6+1e5+1e4,M = 1e5+10,INF = 0x3f3f3f3f,mod = 1e9+7;
const ll MOD = 212370440130137957ll;//hash(hight)
const int base = 131;
const double eps = 1e-3;
const int seed=10086,mo=1e6+7; //hash(lower)
int prime = 233317;
ll n,q,dfncnt = 0;
ll f[N][23],dep[N],rec[N][23],dfn[N],Log[N],id1[N],id2[N];
vector<vector<Pll>> g(N+1);
Pll a[N];
void dfs(ll u,ll pa){
	f[++dfncnt][0] = dep[u];
	rec[dfncnt][0] = u;
	dfn[u] = dfncnt;
	for(auto [v,w]:g[u]){
		if(v == pa ) continue;
		dep[v] = dep[u]+w;
		dfs(v,u);
		f[++dfncnt][0] = dep[u];
		rec[dfncnt][0] = u;
	}
}
ll ask(ll l,ll r){
    ll k = Log[r-l+1];
    if(f[l][k] < f[r-(1<<k)+1][k]) return rec[l][k];
    else return rec[r-(1<<k)+1][k];
}
ll lca(ll x,ll y){
    if(dfn[x]>dfn[y]) swap(x,y);
    return ask(dfn[x],dfn[y]);
}
ll dis(ll x,ll y){
    //cout<<lca(x,y)<<'\n';
    return dep[x]+dep[y]-2*1ll*dep[lca(x,y)];
}
void solve(){	
	cin>>n>>q;
	Log[0] = -1;for(int i = 1;i<N;i++) Log[i] = Log[i>>1]+1; 
	fa(i,1,n) cin>>a[i].fi,a[i].se = i;
	sort(a+1,a+1+n);
	for(int i = 1;i<n;i++){
		ll u,v,w;cin>>u>>v>>w;
		g[u].pb({v,w}),g[v].pb({u,w});
	}
	if(a[1].fi != 0){
		while(q--) cout<<0<<'\n';
		return ;
	} 
	id1[1] = id2[1] = a[1].se;
	dfs(a[1].se,0);
    for(int k=1;k<=22;k++) {
        for(int i=1;i+(1<<k-1)<=dfncnt;i++) {
            if(f[i][k-1] < f[i+(1<<k-1)][k-1])
                f[i][k] = f[i][k-1], rec[i][k] = rec[i][k-1];
            else
                f[i][k] = f[i+(1<<k-1)][k-1], rec[i][k] = rec[i+(1<<k-1)][k-1];
        }
    }
	ll da = 1;
	for(int i = 2;i<=n;i++){
		if(a[i].fi != i-1) break;
		da = i;
		id1[i] = id1[i-1];
		id2[i] = id2[i-1];
		ll dis1 = dis(id1[i],id2[i]);
		ll dis2 = dis(id1[i],a[i].se);
		ll dis3 = dis(id2[i],a[i].se);
		if(dis2>dis1||dis3>dis1){
			if(dis2>dis1) id2[i] = a[i].se;
			else id1[i] = a[i].se;
		}
	}
	while(q--){
		ll x,y;cin>>x>>y;
		if(dis(x,id1[da])<=y&&dis(x,id2[da])<=y) cout<<da<<'\n';
		else if(dis(x,id1[1])>y) cout<<0<<'\n';
		else {
			ll l = 1,r = da-1,ans;
			while(l<=r){
				ll  mid = (l+r)>>1;
				if(dis(x,id1[mid])<=y&&dis(x,id2[mid])<=y){
				 	ans = mid,l = mid+1;
				}else{
					r = mid-1;
				}
			}
			cout<<ans<<'\n';
		}
	}
	return ;
}	

int main()
{
	ios::sync_with_stdio(0),cin.tie(0),cout.tie(0);
	int t = 1;
	//cin>>t;
	while(t--){
		solve();
	}
	return 0;
}
/**/