Hi, I'm writing a program in fortran that basically creates a loop from 1 until a certain number x (input by the user), and goes through each value between 1 and the certain number x in order to determine if each value meets certain criteria. The criteria is that the sum of the square of the individual digits created by each value in between 1 and x (where each value is taken from the preceding sum), must eventually equal 1. For example, the number 7 meets this criteria, because when we take the sum of the square of the individual digits, (7^2)=49, (4^2)+(9^2)=97, (9^2)+(7^2)=130, (1^2)+(3^2)+(0^2)=10, (1^2)+(0^2)= 1. The same goes for the number 13, except this reaches 1 after only two steps: (1^2)+(3^2)=10, (1^2)+(0^2)= 1. I have already wrote the program for calculating the sum of the square of the individual digits of a number, and eventually reaching 1. Although I am having trouble finding a function to use in order to go through each number from 1 to a certain value x, and determining whether each number in between 1 and x meets this criteria or not. Any help would be appreciated! Thanks!