/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:3:6: warning: return type of 'main' is not 'int' [-Wmain]
 void main(){
      ^~~~
/in/foo.c: In function 'main':
/in/foo.c:5:16: error: invalid operands to binary & (have 'int *' and 'int')
 scanf("%d%d",&a&b);
              ~~^