A is a natural number .if A subtracts 1,3,5...(some continou

A is a natural number .if A subtracts 1,3,5...(some continous odd numbers )until it cannot subtract more ,the result will be 29 ;if A subtracts 2,4,6...(some continous even numbers )until it cannot subtract more ,the result will be 13 .so what is A 紧急!