Step 1: Divide the number into separate digits:
7277 => 7 2 7 7
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
7 to 2 = 5
2 to 7 = 5
7 to 7 = 0
7 to 7 = 0
Step 3: Combine the filters to a string:
5 5 0 0 = 5500