The round is over, I hope you have enjoyed it. Here is the editorial.
The language of this round is COBOL (dialect COBOL85), one of the oldest programming languages (date of “birth”: 1959, so it’s twice older than I am). Despite being so old, it’s still in active use, though not in programming competitions, so I think it should be enough of a surprise for you :-)
The problem "A+B" (numbers A and B given in separate lines) can be solved in a following way:
IDENTIFICATION DIVISION. PROGRAM-ID. SOLUTION. DATA DIVISION. WORKING-STORAGE SECTION. 01 A PIC 9(10) VALUE ZEROES. 01 B PIC 9(10) VALUE ZEROES. 01 STR PIC X(10). PROCEDURE DIVISION. ACCEPT STR MOVE STR TO A ACCEPT STR MOVE STR TO B ADD A TO B DISPLAY B STOP RUN.