The Return of the Roman Empire 

Input and Output 

Write a program that accepts Roman numerals (one per line) and converts them to decimal form.

Remember, I=1, V=5, X=10, L=50, C=100, D=500, and M=1000. Furthermore, there are the following digraphs: IV=4, IX=9, XL=40, XC=90, CD=400, CM=900.

The program should reject improperly formed numerals.

Sample Input 

MCMXCVIII
CCM

Sample Output 

1998
This is not a valid number