#include<cstdio>

#define min(a,b) (a<b?a:b)

#define max(a,b) (a>b?a:b)

#define swap(a,b) (a^=b,b^=a,a^=b)

using namespace std;

const int mm=;

const int mn=;

int s[mm],t[mm],d[mm],p[mm],ans[mm];

int h[mn]={},q[mn]={},g[mn]={},f[mn],mx[mn],mi[mn],up[mn]={},dw[mn]={};

bool vis[mn]={};

int i,j,k,n,m,e;

inline void add(int u,int v,int c,int h[])

{

    s[e]=u,t[e]=v,d[e]=c,p[e]=h[u],h[u]=e++;

    s[e]=v,t[e]=u,d[e]=-c,p[e]=h[v],h[v]=e++;

}

int find(int x)

{

    if(f[x]==x)return x;

    int y=f[x];

    f[x]=find(f[x]);

    up[x]=max(mx[y]-mi[x],max(up[x],up[y]));

    dw[x]=max(mx[x]-mi[y],max(dw[x],dw[y]));

    mx[x]=max(mx[x],mx[y]);

    mi[x]=min(mi[x],mi[y]);

    return f[x];

}

void tarjan(int u)

{

    int i,v,x,y;

    vis[f[u]=u]=;

    for(i=q[u];i;i=p[i])

        if(vis[v=t[i]])

            v=find(v),t[e]=i,p[e]=g[v],g[v]=e++;

    for(i=h[u];i;i=p[i])

        if(!vis[v=t[i]])tarjan(v),f[v]=u;

    for(i=g[u];i;i=p[i])

    {

        v=t[i],x=s[v],y=t[v],find(x);

        if(d[v]<)swap(x,y),v=-d[v];

        else v=d[v];

        ans[v]=max(mx[y]-mi[x],max(up[x],dw[y]));

    }

}

inline void get(int &a)

{

    char c;

    while((c=getchar())<''||c>'');

    for(a=;c>=''&&c<='';c=getchar())a=a*+c-'';

}

void out(int x)

{

    if(x>)out(x/);

    putchar(x%+'');

}

int main()

{

    for(get(n),i=; i<=n; ++i)get(mx[i]),mi[i]=mx[i];

    for(e=k=; k<n; ++k)get(i),get(j),add(i,j,,h);

    for(get(m),k=; k<=m; ++k)get(i),get(j),add(i,j,k,q);

    tarjan();

    for(i=; i<=m; ++i)out(ans[i]),puts("");

    return ;

}