McCarthy is a famous theorician of computer science. In his work, he defined a recursive function, called f91, that takes as input a positive integer N and returns a positive integer defined as follows:
Write a program, that computes McCarthy's f91.
The input tests will consist of a series of positive integers, each integer is at most 1,000,000. There will be at most 250,000 test cases. Each number is on a line on its own. The end of the input is reached when the number 0 is met. The number 0 shall not be considered as part of the test set.
The program shall output each result on a line by its own, following the format given in the sample output.
500 91 0
f91(500) = 490 f91(91) = 91