import bisect
import sys
input = sys.stdin.readline
T = int(input())
for _ in range(T):
    N, L = map(int, input().split())
    XY = [list(map(int, input().split())) for _ in range(N)]
    Z = [[[] for _ in range(41)] for _ in range(41)]
    D = [0 for _ in range(41)]
    D[40] = L+1
    for i in range(1, 40):
        D[i] = int(L/40*i)
    for i in range(N):
        x, y = XY[i]
        xpos = bisect.bisect_left(D, x)
        ypos = bisect.bisect_left(D, y)
        Z[xpos][ypos].append(i)
    ans = []
    for i in range(41):
        for j in range(41):
            if i%2==0:
                k = j
            else:
                k = 39-j
            for l in Z[i][j]:
                ans.append(XY[l])
    print(len(ans))
    for a in ans:
        print(*a)