/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: In function 'main':
/in/foo.c:7:5: error: 'cin' undeclared (first use in this function)
cin>>T;
^~~
/in/foo.c:7:5: note: each undeclared identifier is reported only once for each function it appears in
/in/foo.c:12:6: error: 'cout' undeclared (first use in this function)
cout<<a<<endl;
^~~~
/in/foo.c:12:15: error: 'endl' undeclared (first use in this function)
cout<<a<<endl;
^~~~