I feared that the problems would become harder and harder, and after solving problem 88 I feared Problem 89 of Project Euler. Luckily for me I was wrong, problem 89 is not that difficult. The problem reads

The rules for writing Roman numerals allow for many ways of writing each number (see About Roman Numerals…). However, there is always a “best” way of writing a particular number.

For example, the following represent all of the legitimate ways of writing the number sixteen:

IIIIIIIIIIIIIIII

VIIIIIIIIIII

VVIIIIII

XIIIIII

VVVI

XVI

The last example being considered the most efficient, as it uses the least number of numerals.

The 11K text file, roman.txt contains one thousand numbers written in valid, but not necessarily minimal, Roman numerals; that is, they are arranged in descending units and obey the subtractive pair rule (see About Roman Numerals… for the definitive rules for this problem).

Find the number of characters saved by writing each of these in their minimal form.

Note: You can assume that all the Roman numerals in the file contain no more than four consecutive identical units.