#include <cstdio>

 #include <cstring>

 #include <iostream>

 #define N 2000001

 #define Min(x, y) ((x) < (y) ? (x) : (y))

 #define Max(x, y) ((x) > (y) ? (x) : (y))

 #define swap(x, y) ((x) ^= (y) ^= (x) ^= (y))

 int n, m, cnt, qcnt, acnt;

 int f[N], fa[N], max[N], min[N], up[N], down[N], ans[N];

 int head[N], to[N << ], next[N << ], qhead[N], qu[N << ], qv[N << ], qid[N << ], qnext[N << ], ahead[N], ato[N << ], anext[N << ];

 inline int read()

 {

     int x = , f = ;

     char ch = getchar();

     for(; !isdigit(ch); ch = getchar()) if(ch == '-') f = -;

     for(; isdigit(ch); ch = getchar()) x = (x << ) + (x << ) + ch - '';

     return x * f;

 }

 inline void add(int x, int y)

 {

     to[cnt] = y;

     next[cnt] = head[x];

     head[x] = cnt++;

 }

 inline void add_ask(int x, int y, int z)

 {

     qu[qcnt] = x;

     qv[qcnt] = y;

     qid[qcnt] = z;

     qnext[qcnt] = qhead[x];

     qhead[x] = qcnt++;

 }

 inline void add_ans(int x, int y)

 {

     ato[acnt] = y;

     anext[acnt] = ahead[x];

     ahead[x] = acnt++;

 }

 inline int find(int x)

 {

     if(x ^ f[x])

     {

         int fx = f[x];

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

         up[x] = Max(up[x], Max(up[fx], max[fx] - min[x]));

         down[x] = Max(down[x], Max(down[fx], max[x] - min[fx]));

         max[x] = Max(max[fx], max[x]);

         min[x] = Min(min[fx], max[x]);

     }

     return f[x];

 }

 inline void dfs(int u)

 {

     int i, v, x, y;

     f[u] = u;

     for(i = qhead[u]; i ^ -; i = qnext[i])

         if(f[qv[i]])

         {

             x = find(qv[i]);

             add_ans(x, i);

         }

     for(i = head[u]; i ^ -; i = next[i])

     {

         v = to[i];

         if(v ^ fa[u]) fa[v] = u, dfs(v);

     }

     for(i = ahead[u]; i ^ -; i = anext[i])

     {

         x = qu[ato[i]];

         y = qv[ato[i]];

         find(x), find(y);

         if(ato[i] & ) swap(x, y);

         ans[qid[ato[i]]] = Max(max[y] - min[x], Max(up[x], down[y]));

     }

     f[u] = fa[u];

 }

 int main()

 {

     int i, j, x, y;

     while(~scanf("%d", &n))

     {

         cnt = qcnt = acnt = ;

         memset(head, -, sizeof(head));

         memset(qhead, -, sizeof(qhead));

         memset(ahead, -, sizeof(ahead));

         memset(f, , sizeof(f));

         memset(fa, , sizeof(fa));

         memset(ans, , sizeof(ans));

         for(i = ; i <= n; i++) min[i] = max[i] = read(), up[i] = down[i] = ;

         for(i = ; i < n; i++)

         {

             x = read();

             y = read();

             add(x, y);

             add(y, x);

         }

         m = read();

         for(i = ; i <= m; i++)

         {

             x = read();

             y = read();

             add_ask(x, y, i);

             add_ask(y, x, i);

         }

         dfs();

         for(i = ; i <= m; i++) printf("%d\n", ans[i]);

     }

     return ;

 }