TO Insert Space in place of missing letter

[Guptarupesh09]

I need to insert the space in place of missing letter in the file. There are records as per below:

abcdefgh......zabcdef....
abcdehi.....zabcdh....
adhei.......abc...

If you see the first rec is from a-z then again from a and so on but second rec has fand g missing. SO I want to insert two spaces in between them and for the other records as well. need advise