Step 1: Divide the number into separate digits:
1970 => 1 9 7 0
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
1 to 9 = 8
9 to 7 = 2
7 to 0 = 7
0 to 1 = 1
Step 3: Combine the filters to a string:
8 2 7 1 = 8271