Python - 2 lines
\nclass Solution:\n    def lengthAfterTransformations(self, s, t):\n        @cache\n        def count(c): return 1 if c < 26 else (count(c - 26) + count(c - 25)
```\nclass Solution:\n    def lengthAfterTransformations(self, s, t):\n        @cache\n        def count(c): return 1 if c < 26 else (count(c - 26) + count(c - 25)) % 1_000_000_007\n        return sum(count(t + ord(c) - ord(\'a\'))%1_000_000_007 for c in s) % 1_000_000_007\n```
['Python3']