/in/foo.c:2:1: warning: data definition has no type or storage class
 output(int a[10000],int n);
 ^~~~~~
/in/foo.c:2:1: warning: type defaults to 'int' in declaration of 'output' [-Wimplicit-int]
/in/foo.c:11:1: warning: return type defaults to 'int' [-Wimplicit-int]
 output(int a[10000],int n)
 ^~~~~~