T={M:1e3,CM:900,D:500,CD:400,C:100,XC:90,L:50,XL:40,X:10,IX:9,V:5,IV:4,I:1}
n=0
`dd`.scan(/#{T.keys*?|}/){n+=T[$&.intern]}
n>3999?$><<:ERROR:while(c,i=T.find{|c,i|i<=n});$><<c;n-=i end