import sys sys.setrecursionlimit(200005) # sys.set_int_max_str_digits(200005) int1 = lambda x: int(x)-1 pDB = lambda *x: print(*x, end="\n", file=sys.stderr) p2D = lambda x: print(*x, sep="\n", end="\n\n", file=sys.stderr) def II(): return int(sys.stdin.readline()) def LI(): return list(map(int, sys.stdin.readline().split())) def LLI(rows_number): return [LI() for _ in range(rows_number)] def LI1(): return list(map(int1, sys.stdin.readline().split())) def LLI1(rows_number): return [LI1() for _ in range(rows_number)] def SI(): return sys.stdin.readline().rstrip() dij = [(0, 1), (-1, 0), (0, -1), (1, 0)] # dij = [(0, 1), (-1, 0), (0, -1), (1, 0), (1, 1), (1, -1), (-1, 1), (-1, -1)] # inf = -1-(-1 << 31) inf = -1-(-1 << 62) # md = 10**9+7 md = 998244353 from collections import defaultdict def solve(): n,L=LI() xy=LLI(n) h = L//round(n**0.5) i2xy=defaultdict(list) for x,y in xy: i=x//h i2xy[i].append((x,y)) ans=[] rev=0 for i in sorted(i2xy): i2xy[i].sort(key=lambda x:x[1],reverse=rev) rev^=1 ans+=i2xy[i] print(len(ans)) for x,y in ans:print(x,y) for _ in range(II()):solve()