Problem 1879. Converting numbers back from extended form

Thanks for all the help you guys gave me on writing out the numbers in extended form in Problem 1871. I got so good at it thanks to your help, now my teacher wants me to do the opposite. She's going to give me the number in extended form, and she wants me to write it out normally. In this case, the string '10000+200+30+4' would be the input, and the output would be the number 10234.

First I expand the number, and then I contract it. I wish she could just make up her mind!