Step 1: Divide the number into separate digits:
9292 => 9 2 9 2
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
9 to 2 = 7
2 to 9 = 7
9 to 2 = 7
2 to 9 = 7
Step 3: Combine the filters to a string:
7 7 7 7 = 7777