CF381B Sereja and Stairs

Sereja loves integer sequences very much. He especially likes stairs. Sequence $ a_{1},a_{2},...,a_{|a|} $ ( $ |a| $ is the length of the sequence) is stairs if there is such index $ i $ $ (1

The first line contains integer $ m $ $ (1

In the first line print the number of cards you can put on the table. In the second line print the resulting stairs.