T=int(input())
for i in range(T):
	N,M=map(int,input().split())
	if N%4==0 and M%2==0:
		print(N*M//4)
		ans=[[0]*M for i in range(N)]
		cnt=1
		for i in range(0,N,4):
			for j in range(0,M,2):
				ans[i][j]=cnt
				ans[i][j+1]=cnt
				ans[i+1][j]=cnt
				ans[i+2][j]=cnt
				ans[i+3][j]=cnt+1
				ans[i+3][j+1]=cnt+1
				ans[i+2][j+1]=cnt+1
				ans[i+1][j+1]=cnt+1
				cnt+=2
		for i in ans:
			print(*i)
	elif N%2==0 and M%4==0:
		print(N*M//4)
		ans=[[0]*M for i in range(N)]
		cnt=1
		for i in range(0,M,4):
			for j in range(0,N,2):
				ans[j][i]=cnt
				ans[j+1][i]=cnt
				ans[j][i+1]=cnt
				ans[j][i+2]=cnt
				ans[j][i+3]=cnt+1
				ans[j+1][i+3]=cnt+1
				ans[j+1][i+2]=cnt+1
				ans[j+1][i+1]=cnt+1
				cnt+=2
		for i in ans:
			print(*i)
	elif N%8==0 and M>=3:
		print(N*M//4)
		ans=[[0]*M for i in range(N)]
		cnt=1
		for i in range(0,N,8):
			ans[i][0]=cnt
			ans[i][1]=cnt
			ans[i][2]=cnt
			ans[i+1][0]=cnt
			cnt+=1
			ans[i+1][1]=cnt
			ans[i+1][2]=cnt
			ans[i+2][2]=cnt
			ans[i+3][2]=cnt
			cnt+=1
			ans[i+2][0]=cnt
			ans[i+2][1]=cnt
			ans[i+3][1]=cnt
			ans[i+4][1]=cnt
			cnt+=1
			ans[i+3][0]=cnt
			ans[i+4][0]=cnt
			ans[i+5][0]=cnt
			ans[i+5][1]=cnt
			cnt+=1
			ans[i+4][2]=cnt
			ans[i+5][2]=cnt
			ans[i+6][2]=cnt
			ans[i+6][1]=cnt
			cnt+=1
			ans[i+6][0]=cnt
			ans[i+7][0]=cnt
			ans[i+7][1]=cnt
			ans[i+7][2]=cnt
			cnt+=1
		for i in range(0,N,4):
			for j in range(3,M,2):
				ans[i][j]=cnt
				ans[i][j+1]=cnt
				ans[i+1][j]=cnt
				ans[i+2][j]=cnt
				ans[i+3][j]=cnt+1
				ans[i+3][j+1]=cnt+1
				ans[i+2][j+1]=cnt+1
				ans[i+1][j+1]=cnt+1
				cnt+=2
		for i in ans:
			print(*i)
	elif M%8==0 and N>=3:
		print(N*M//4)
		N,M=M,N
		ans=[[0]*M for i in range(N)]
		cnt=1
		for i in range(0,N,8):
			ans[i][0]=cnt
			ans[i][1]=cnt
			ans[i][2]=cnt
			ans[i+1][0]=cnt
			cnt+=1
			ans[i+1][1]=cnt
			ans[i+1][2]=cnt
			ans[i+2][2]=cnt
			ans[i+3][2]=cnt
			cnt+=1
			ans[i+2][0]=cnt
			ans[i+2][1]=cnt
			ans[i+3][1]=cnt
			ans[i+4][1]=cnt
			cnt+=1
			ans[i+3][0]=cnt
			ans[i+4][0]=cnt
			ans[i+5][0]=cnt
			ans[i+5][1]=cnt
			cnt+=1
			ans[i+4][2]=cnt
			ans[i+5][2]=cnt
			ans[i+6][2]=cnt
			ans[i+6][1]=cnt
			cnt+=1
			ans[i+6][0]=cnt
			ans[i+7][0]=cnt
			ans[i+7][1]=cnt
			ans[i+7][2]=cnt
			cnt+=1
		for i in range(0,N,4):
			for j in range(3,M,2):
				ans[i][j]=cnt
				ans[i][j+1]=cnt
				ans[i+1][j]=cnt
				ans[i+2][j]=cnt
				ans[i+3][j]=cnt+1
				ans[i+3][j+1]=cnt+1
				ans[i+2][j+1]=cnt+1
				ans[i+1][j+1]=cnt+1
				cnt+=2
		ans=[list(x) for x in zip(*ans)]
		for i in ans:
			print(*i)
	else:
		print(-1)