vbuiglllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllll
= 900 00 + 900 0001 + 900 002 + 900 0003 + 900 004 + 900 005+ ... + 1 000 000 + 1 000 001 + 1 000 0002 + 1 000 003 + 1 000 004 + 1 000 005 nhé bn