import std.conv, std.functional, std.range, std.stdio, std.string;
import std.algorithm, std.array, std.bigint, std.bitmanip, std.complex, std.container, std.math, std.mathspecial, std.numeric, std.regex, std.typecons;
import core.bitop;

class EOFException : Throwable { this() { super("EOF"); } }
string[] tokens;
string readToken() { for (; tokens.empty; ) { if (stdin.eof) { throw new EOFException; } tokens = readln.split; } auto token = tokens.front; tokens.popFront; return token; }
int readInt() { return readToken.to!int; }
long readLong() { return readToken.to!long; }

string COLOR(string s = "") { return "\x1b[" ~ s ~ "m"; }

bool chmin(T)(ref T t, in T f) { if (t > f) { t = f; return true; } else { return false; } }
bool chmax(T)(ref T t, in T f) { if (t < f) { t = f; return true; } else { return false; } }

int binarySearch(alias pred, T)(in T[] as) { int lo = -1, hi = cast(int)(as.length); for (; lo + 1 < hi; ) { const mid = (lo + hi) >> 1; (unaryFun!pred(as[mid]) ? hi : lo) = mid; } return hi; }
int lowerBound(T)(in T[] as, T val) { return as.binarySearch!(a => (a >= val)); }
int upperBound(T)(in T[] as, T val) { return as.binarySearch!(a => (a > val)); }


int[][] solve(int M, int N) {
  if ((M * N) % 8 != 0) return null;
  if (M == 1) return null;
  if (N == 1) return null;
  if (N % 4 != 0) {
    const aa = solve(N, M);
    auto a = new int[][](M, N);
    foreach (x; 0 .. M) foreach (y; 0 .. N) a[x][y] = aa[y][x];
    return a;
  }
  auto a = new int[][](M, N);
  int k;
  int x;
  if (M & 1) {
    assert(N % 8 == 0);
    enum PAT = [
      [0, 0, 2, 2, 2, 3, 5, 5],
      [0, 1, 2, 3, 3, 3, 4, 5],
      [0, 1, 1, 1, 4, 4, 4, 5],
    ];
    for (int y = 0; y < N; y += 8) {
      foreach (dx; 0 .. 3) foreach (dy; 0 .. 8) a[x + dx][y + dy] = k + PAT[dx][dy];
      k += 6;
    }
    x += 3;
  }
  assert((M - x) % 2 == 0);
  assert(N % 4 == 0);
  for (; x < M; x += 2) {
    for (int y = 0; y < N; y += 4) {
      a[x][y] = a[x][y + 1] = a[x][y + 2] = a[x + 1][y] = k++;
      a[x][y + 3] = a[x + 1][y + 1] = a[x + 1][y + 2] = a[x + 1][y + 3] = k++;
    }
  }
  return a;
}

void main() {
  try {
    for (; ; ) {
      const numCases = readInt;
      foreach (caseId; 0 .. numCases) {
        const M = readInt;
        const N = readInt;
        
        const ans = solve(M, N);
        if (ans) {
          writeln((M * N) / 4);
          foreach (x; 0 .. M) {
            foreach (y; 0 .. N) {
              if (y) write(" ");
              write(ans[x][y] + 1);
            }
            writeln;
          }
        } else {
          writeln(-1);
        }
      }
    }
  } catch (EOFException e) {
  }
}