Problem with method

[sarpulhu]

I think heads and tails are two different size lists so probably of each word is not equal? Also I think removing past 4362 means first digit 4 is different size then first digit 3.

Example I found that doesn't have group problem: https://gist.github.com/sarpulhu/6e7dd35c34c5ee45176001320f1a0eed