/in/foo.c:2:6: warning: return type of 'main' is not 'int' [-Wmain]
 void main()
      ^~~~
/in/foo.c: In function 'main':
/in/foo.c:6:10: warning: format '%d' expects argument of type 'int *', but argument 2 has type 'int' [-Wformat=]
  scanf("%d",num);
          ^
/in/foo.c:9:11: warning: format '%d' expects argument of type 'int *', but argument 2 has type 'int' [-Wformat=]
   scanf("%d",a[i]);
           ^