/in/foo.c:2:1: error: unknown type name 'using'
 using namespace std;
 ^~~~~
/in/foo.c:2:17: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'std'
 using namespace std;
                 ^~~
/in/foo.c:3:19: error: 'n' undeclared here (not in a function)
 void Output(int a[n],int n)
                   ^
/in/foo.c: In function 'Output':
/in/foo.c:6:3: error: 'cout' undeclared (first use in this function)
   cout<<a[i]<<"";
   ^~~~
/in/foo.c:6:3: note: each undeclared identifier is reported only once for each function it appears in
/in/foo.c:7:8: error: 'endl' undeclared (first use in this function)
  cout<<endl;
        ^~~~
/in/foo.c: In function 'main':
/in/foo.c:12:2: error: 'cin' undeclared (first use in this function)
  cin>>n;
  ^~~
/in/foo.c:14:3: error: 'cout' undeclared (first use in this function)
   cout<<a[i]<<"";
   ^~~~
/in/foo.c:15:9: error: type of formal parameter 1 is incomplete
  Output(a,n);
         ^