foo.c:2:1: error: unknown type name 'using'
2 | using namespace std;
| ^~~~~
foo.c:2:17: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'std'
2 | using namespace std;
| ^~~
foo.c: In function 'main':
foo.c:6:9: error: 'cin' undeclared (first use in this function)
6 | cin>>x>>y;
| ^~~
foo.c:6:9: note: each undeclared identifier is reported only once for each function it appears in
foo.c:7:9: error: 'cout' undeclared (first use in this function)
7 | cout<<x+y;
| ^~~~
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