Bear and Row 01

Limak is a little polar bear. He is playing a video game and he needs your help. There is a row with N cells, each either empty or occupied by a soldier, denoted by '0' and '1' respectively. The goal of the game is to move all soldiers to the right (they should occupy some number of rightmost cells). The only possible command is choosing a soldier and telling him to move to the right as far as p