/**
 *    author: sunkuangzheng
 *    created: 11.04.2024 20:01:39
**/
#include<bits/stdc++.h>
#ifdef DEBUG_LOCAL
#include <mydebug/debug.h>
#endif
using ll = long long;
const int N = 5e5+5;
using namespace std;
int T,n,m,a[N],ok[N],u,v,w,siz[N],tt,rt,vis[N],au[N],t[N],ans[N],re = 1e9; 
vector<pair<int,int>> g[N]; vector<int> b; 
vector<pair<int,ll>> tp,qu,uq[N]; ll k,dd[N]; vector<ll> ds;
#define ff for(auto [v,w] : g[u]) if(!vis[v] && v != f) 
void upd(int x,int k){for(;x;x -= x & -x) t[x] = min(t[x],k);}
int qry(int x){for(re = 1e9;x <= n;x += x & -x) re = min(re,t[x]); return re;}
void clr(int x){for(;x;x -= x & -x) t[x] = 1e9;}
void dfs1(int u,int f,int sz){
    siz[u] = 1; int mx = 0;
    ff dfs1(v,u,sz),siz[u] += siz[v],mx = max(mx,siz[v]);
    if(mx = max(mx,sz - siz[u]),mx < tt) tt = mx,rt = u;
}void dfs2(int u,int f,ll d,int op){
    tp.emplace_back(a[u],d),dd[u] = d; if(op) ds.push_back(d);
    for(auto i : uq[u]) qu.emplace_back(i);
    ff dfs2(v,u,d+w,op);
}void solve(int u){
    tp.clear(),qu.clear(),ds.clear(),dfs2(u,0,0,1); int f = 0; ds.push_back(1e14+5);
    sort(ds.begin(),ds.end()),ds.erase(unique(ds.begin(),ds.end()));
    for(auto &[x,k] : tp) if(k) k = lower_bound(ds.begin(),ds.end(),k) - ds.begin() + 1,upd(k,x);
    qu.clear(); for(auto i : uq[u]) qu.push_back(i);
    for(auto &[x,k] : qu) k = lower_bound(ds.begin(),ds.end(),k+1) - ds.begin() + 1,ans[x] = min(ans[x],qry(k));
    for(int i = 1;i <= ds.size();i ++) t[i] = 1e9;upd(1,a[u]);
    ff{
        tp.clear(),qu.clear(),dfs2(v,u,w,0);
        for(auto &[x,k] : qu) k = lower_bound(ds.begin(),ds.end(),k+1-dd[au[x]]) - ds.begin() + 1,ans[x] = min(ans[x],qry(k));
        for(auto &[x,k] : tp) k = lower_bound(ds.begin(),ds.end(),k) - ds.begin() + 1,upd(k,x);
    }for(int i = 1;i <= ds.size();i ++) t[i] = 1e9;
    reverse(g[u].begin(),g[u].end());
    ff{
        tp.clear(),qu.clear(),dfs2(v,u,w,0);
        for(auto &[x,k] : qu) k = lower_bound(ds.begin(),ds.end(),k+1-dd[au[x]]) - ds.begin() + 1,ans[x] = min(ans[x],qry(k));
        for(auto &[x,k] : tp) k = lower_bound(ds.begin(),ds.end(),k) - ds.begin() + 1,upd(k,x);
    }for(int i = 1;i <= ds.size();i ++) t[i] = 1e9;
    reverse(g[u].begin(),g[u].end());
}void dfs2(int u,int f){solve(u),vis[u] = 1; ff tt = 1e9,dfs1(v,u,siz[v]),dfs2(rt,0);}
int main(){
    ios::sync_with_stdio(0),cin.tie(0);
    cin >> n >> m; 
    for(int i = 1;i <= n;i ++)
        if(cin >> a[i],b.push_back(a[i]),a[i] <= n) ok[a[i]] = 1;
    int mex = 0; while(ok[mex]) mex ++;
    fill(ans+1,ans+m+1,mex),fill(t+1,t+n+1,1e9);
    for(int i = 1;i < n;i ++) cin >> u >> v >> w,g[u].emplace_back(v,w),g[v].emplace_back(u,w);
    for(int i = 1;i <= m;i ++) cin >> u >> k,au[i] = u,uq[u].emplace_back(i,k);
    tt = 1e9,dfs1(1,0,n),dfs2(rt,0);
    for(int i = 1;i <= m;i ++) cout << ans[i] << "\n";
}