/in/foo.c: In function 'PrimeNum':
/in/foo.c:23:22: warning: implicit declaration of function 'exit' [-Wimplicit-function-declaration]
         if(n%j == 0) exit(0);
                      ^~~~
/in/foo.c:23:22: warning: incompatible implicit declaration of built-in function 'exit'
/in/foo.c:23:22: note: include '<stdlib.h>' or provide a declaration of 'exit'