#include<bits/stdc++.h>
using namespace std;
long long n,q,st[20][100010],a[100010],u,v,w,ans,r[1010][1010],x,lca,dis,tot,flag,son[200010];
struct node
{
    int depth,fa;
    vector<long long>c;
}t[100010];
inline long long read()
{
	long long k=0,f=1;
    char c=getchar();
	for(;!isdigit(c);c=getchar()) if(c=='-') f=-1;
	for(;isdigit(c);c=getchar()) k=(k<<1)+(k<<3)+c-'0';
	return k*f;
}
inline void write(long long x)
{
    if(x<0) putchar('-'),x=-x;
    if(x>9) write(x/10);
    putchar(x%10+'0');
}
inline void dfs(long long x,long long fa)
{
    t[x].depth=t[fa].depth+1;
    st[0][x]=fa;
    for(long long i=1;i<=19;i++) st[i][x]=st[i-1][st[i-1][x]];
    for(long long i=0;i<t[x].c.size();i++)
    {
        long long j=t[x].c[i];
        dfs(j,x);
    }
}
inline long long LCA(long long x,long long y)
{
    if(t[x].depth<t[y].depth) swap(x,y);
    long long h=t[x].depth-t[y].depth;
    for(long long i=19;i>=0;i--) if(h>=(1<<i)) h-=1<<i,x=st[i][x];
    if(x==y) return x;
    for(long long i=19;i>=0;i--) if(st[i][x]!=st[i][y]) x=st[i][x],y=st[i][y];
    return st[0][x];
}
int main()
{
    freopen("poitry.in","r",stdin);
    freopen("poitry.out","w",stdout);
    n=read(),q=read();
    for(long long i=1;i<=n;i++) a[i]=read();
    for(long long i=1;i<n;i++)
    {
        u=read(),v=read(),w=read();
        t[u].c.push_back(v);
        t[v].fa=u;
        r[u][v]=w;
        r[v][u]=w;
        son[v]=w;
        if(u!=1) flag=1;
    }
    if(u==1)
    {
        while(q--)
        {
            u=read(),v=read();
            if(u==1)
            {
                if(v==1) ans=a[1];
                else ans=min(a[1],max(a[v],son[v]));
            }
            else if(v==1)
            {
                ans=min(a[u],max(a[1],son[u]));
            }
            else
            {
                ans=min(a[u],min(max(a[1],son[u]),max(a[v],son[u]+son[v])));
            }
            write(ans);
            cout<<endl;
        }
        return 0;
    }
    dfs(1,0);
    while(q--)
    {
        u=read(),v=read();
        ans=0x7f7f7f7f;
        lca=LCA(u,v);
        tot=0;
        for(x=u;x!=lca;x=t[x].fa)
        {
            ans=min(ans,max(a[x],tot));
            tot+=r[x][t[x].fa];
        }
        ans=min(ans,max(a[x],dis));
        for(x=v;x!=lca;x=t[x].fa) tot+=r[x][t[x].fa];
        dis=0;
        for(x=v;x!=lca;x=t[x].fa)
        {
            ans=min(ans,max(a[x],tot-dis));
            dis+=r[x][t[x].fa];
        }
        write(ans);
        cout<<endl;
    }
    return 0;
}