/in/foo.c: In function 'isprime':
/in/foo.c:18:9: warning: implicit declaration of function 'main' [-Wimplicit-function-declaration]
   18 |         main()
      |         ^~~~
/in/foo.c:18:15: error: expected ';' before '{' token
   18 |         main()
      |               ^
      |               ;
   19 |         {
      |         ~      
/in/foo.c:46:1: error: expected declaration or statement at end of input
   46 | }
      | ^