/in/foo.c: In function 'main':
/in/foo.c:6:5: error: 'original_num' undeclared (first use in this function)
     original_num = num;
     ^~~~~~~~~~~~
/in/foo.c:6:5: note: each undeclared identifier is reported only once for each function it appears in
/in/foo.c:10:9: error: 'reversed_num' undeclared (first use in this function)
         reversed_num = reversed_num * 10 + remainder;
         ^~~~~~~~~~~~