#include<bits/stdc++.h>
using namespace std;
int n,q,a[200010],u,v,w;
int f[10010][10010],ans;
bool p1,p2;
int main(){
	freopen("poitry.in","r",stdin);
	freopen("poitry.out","w",stdout);
	scanf("%d %d",&n,&q);
    for(int i=1;i<=n;i++)
    scanf("%d",&a[i]);
    for(int i=1;i<=n;i++){
    	for(int j=1;j<=n;j++)
    	f[i][j]=1000001;
	}
    for(int i=1;i<n;i++){
    	f[i][i]=0;
    	scanf("%d %d %d",&u,&v,&w);
    	if(u!=1)p1=1;
    	if(v!=u+1)p2=1;
    	f[u][v]=w;f[v][u]=w;
	}f[n][n]=0;
	if(p1==1){
		for(int k=1;k<=n;k++){
			for(int i=1;i<=n;i++)
			for(int j=1;j<=n;j++)
			f[i][j]=min(f[i][j],f[i][k]+f[k][j]);
	    }
	}
	while(q--){
		scanf("%d %d",&u,&v);
		if(p1==0){
			if(u==1||v==1){
				if(v==1)u=v;
				ans=min(max(a[1],f[1][u]),max(a[u],f[1][u]));
			}else{
				ans=min(a[u],max(a[v],f[u][1]+f[1][v]));
				ans=min(ans,max(a[1],f[1][u]));
			}
		}else if(p2==0){
			for(int i=min(u,v);i<=max(u,v);i++){
				if(i==min(u,v))ans=max(a[i],f[u][i]);
				ans=min(ans,max(a[i],f[u][i]));
			}
		}else{
			ans=a[u];
		}
		printf("%d\n",ans);
	}
	return 0;
}