foo.c: In function ‘main’:
foo.c:4:12: error: expected ‘=’, ‘,’, ‘;’, ‘asm’ or ‘__attribute__’ before ‘>>’ token
    4 |         cin>>year>>month,
      |            ^~
foo.c:8:12: error: ‘r4’ undeclared (first use in this function); did you mean ‘r400’?
    8 |         if(r4==0)
      |            ^~
      |            r400
foo.c:8:12: note: each undeclared identifier is reported only once for each function it appears in
foo.c:25:9: error: ‘cout’ undeclared (first use in this function)
   25 |         cout<<day<<endl;
      |         ^~~~
foo.c:25:20: error: ‘endl’ undeclared (first use in this function)
   25 |         cout<<day<<endl;
      |                    ^~~~
foo.c:26:17: error: expected ‘;’ before ‘}’ token
   26 |         return 0
      |                 ^
      |                 ;
   27 | }
      | ~