Write a program that accepts a Roman numerals and converts it 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. Afther last Roman numeral will be a line containing single zero.

浙江理工大学第三届ACM程序设计竞赛