Step 1: Divide the number into separate digits:
1682 => 1 6 8 2
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
1 to 6 = 5
6 to 8 = 2
8 to 2 = 6
2 to 1 = 1
Step 3: Combine the filters to a string:
5 2 6 1 = 5261