foo.cc: In function ‘int num(int, int)’:
foo.cc:11:9: warning: empty parentheses were disambiguated as a function declaration [-Wvexing-parse]
   11 | int main()
      |         ^~
foo.cc:11:9: note: remove parentheses to default-initialize a variable
   11 | int main()
      |         ^~
      |         --
foo.cc:11:9: note: or replace parentheses with braces to value-initialize a variable
foo.cc:12:1: error: a function-definition is not allowed here before ‘{’ token
   12 | {
      | ^
foo.cc:17:2: error: expected ‘}’ at end of input
   17 | }
      |  ^
foo.cc:4:1: note: to match this ‘{’
    4 | {
      | ^
foo.cc:17:2: warning: no return statement in function returning non-void [-Wreturn-type]
   17 | }
      |  ^