#include <bits/stdc++.h>
using namespace std;
const int N = 5e4 + 5;
const int M = 256;
struct edge {
  int nxt, to;
} e[N << 1];
int fir[N], cnt = 0;
int rec[N][M], fa[N], val[N], anc[N], dep[N];
inline void add(int x, int y) {
  e[++cnt] = (edge){fir[x], y};
  fir[x] = cnt;
}
inline void dfs(int x, int pa) {
  fa[x] = pa;
  dep[x] = dep[pa] + 1;
  for (int i = fir[x]; i; i = e[i].nxt)
    if (e[i].to != pa) dfs(e[i].to, x);
  if (dep[x] < M) return;
  int p = x;
  for (int i = 0; i < M; i++) {
    rec[x][((val[p] ^ i) >> 8) ^ 255] =
        max(rec[x][((val[p] ^ i) >> 8) ^ 255], (val[p] ^ i) | (255 << 8));
    p = fa[p];
  }
  anc[x] = p;
  for (int j = 0; j < 8; j++)
    for (int i = 0; i < M; i++)
      if (rec[x][i] == -1) {
        if (~rec[x][i ^ (1 << j)]) rec[x][i] = rec[x][i ^ (1 << j)] ^ (M << j);
      }
}
inline void solve(int x, int pa) {
  int p = x, ans = 0, l = dep[x] - dep[pa] + 1;
  for (int i = 0; i < l / M; i++) {
    ans = max(ans, rec[p][i]);
    p = anc[p];
  }
  for (int i = l / M * M; i < l; i++) {
    ans = max(ans, val[p] ^ i);
    p = fa[p];
  }
  printf("%d\n", ans);
}
int main() {
  int n, q, x, y;
  memset(rec, -1, sizeof(rec));
  scanf("%d%d", &n, &q);
  for (int i = 1; i <= n; i++) scanf("%d", &val[i]);
  for (int i = 1; i < n; i++) {
    scanf("%d%d", &x, &y);
    add(x, y);
    add(y, x);
  }
  dfs(1, 0);
  while (q--) {
    scanf("%d%d", &x, &y);
    solve(y, x);
  }
  return 0;
}
