This is the link to the problem. https://icpcarchive.ecs.baylor.edu/index.php?option=onlinejudge&page=show_problem&problem=2630

Can anyone give some hint on how to solve this.

Would it be correct to say that if we have large number of rows, answer would exist only for few columns ?? Since length of slabs in each row equals L, there has to be enough space to move the slabs, hence if no of rows are fairly large, only few columns can have a solution.