Step 1: Divide the number into separate digits:
6790 => 6 7 9 0
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
6 to 7 = 1
7 to 9 = 2
9 to 0 = 9
0 to 6 = 6
Step 3: Combine the filters to a string:
1 2 9 6 = 1296