Python Question

I need some help in figuring out how to process a text file with number operations as such:

I have to do this recursively and can't use loops and Im not sure how to do this. The required output should be like the following:

0+1 123456 2593 2 2000000000000000 2 3 1+10 10000000000000000+1 12345667890123456789+87 65432109876543210 999999999999999999999+1