Step 1: Divide the number into separate digits:
7026 => 7 0 2 6
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
7 to 0 = 7
0 to 2 = 2
2 to 6 = 4
6 to 7 = 1
Step 3: Combine the filters to a string:
7 2 4 1 = 7241