/in/foo.c:2:1: error: unknown type name 'using'
    2 | using namespace std；
      | ^~~~~
/in/foo.c:2:17: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'std\U0000ff1b'
    2 | using namespace std；
      |                 ^~~~~
/in/foo.c: In function 'main':
/in/foo.c:13:5: error: 'cin' undeclared (first use in this function)
   13 |     cin>>a>>b;
      |     ^~~
/in/foo.c:13:5: note: each undeclared identifier is reported only once for each function it appears in
/in/foo.c:23:13: warning: implicit declaration of function 'isLeapYear' [-Wimplicit-function-declaration]
   23 |         if (isLeapYear(year))
      |             ^~~~~~~~~~
/in/foo.c:28:5: error: 'cout' undeclared (first use in this function)
   28 |     cout <<n<< endl;
      |     ^~~~
/in/foo.c:28:16: error: 'endl' undeclared (first use in this function)
   28 |     cout <<n<< endl;
      |                ^~~~