import sys
a = []
for l in sys.stdin:
     a.append(l.rstrip('\n'))
# input 
if 0>int(a[0].split()[0]): 
    print(-1)
    exit()

num = 1
count = 1;
alreadyUsedNums = {0}
while True: 
  s = []
  zz = num
  if num in alreadyUsedNums:
      print(-1)
      exit()

  alreadyUsedNums.add(num)

  while True:
    s.append(int(zz%2))
    zz = zz/2
    if zz < 1: break

  num = num - s.count(1) if num + s.count(1) > int(a[0].split()[0]) else num + s.count(1)
  print(num, count)
  count += 1
  if num == int(a[0].split()[0]): break

print(count)
#print(s)