/in/foo.c: In function 'main':
/in/foo.c:5:6: error: expected expression before ':' token
  std::cin>>a>>b;
      ^
/in/foo.c:6:2: error: duplicate label 'std'
  std::cout<<a+b;
  ^~~
/in/foo.c:5:2: note: previous definition of 'std' was here
  std::cin>>a>>b;
  ^~~
/in/foo.c:6:6: error: expected expression before ':' token
  std::cout<<a+b;
      ^
/in/foo.c:5:2: warning: label 'std' defined but not used [-Wunused-label]
  std::cin>>a>>b;
  ^~~
/in/foo.c:4:8: warning: unused variable 'b' [-Wunused-variable]
  int a,b;
        ^
/in/foo.c:4:6: warning: unused variable 'a' [-Wunused-variable]
  int a,b;
      ^