0 : from       0 to 1999999 (2000000)
 1 : from 2000000 to 3999999 (2000000)
 2 : from 4000000 to 5999999 (2000000)
 3 : from 6000000 to 7999998 (1999999)
 4 : from 7999999 to 9999997 (1999999)