/in/foo.c: In function 'main':
/in/foo.c:8:13: error: lvalue required as left operand of assignment
   {if(year%4=0)
             ^
/in/foo.c:9:68: error: lvalue required as left operand of assignment
    {if(month=1||month=3||month=5||month=7||month=8||month=10||month=12)
                                                                    ^
/in/foo.c:11:40: error: lvalue required as left operand of assignment
     if(month=4||month=6||month=9||month=11)
                                        ^
/in/foo.c:18:15: error: lvalue required as left operand of assignment
   {if(year%400=0)
               ^
/in/foo.c:19:68: error: lvalue required as left operand of assignment
    {if(month=1||month=3||month=5||month=7||month=8||month=10||month=12)
                                                                    ^
/in/foo.c:21:40: error: lvalue required as left operand of assignment
     if(month=4||month=6||month=9||month=11)
                                        ^
/in/foo.c:28:67: error: lvalue required as left operand of assignment
   {if(month=1||month=3||month=5||month=7||month=8||month=10||month=12)
                                                                   ^
/in/foo.c:30:38: error: lvalue required as left operand of assignment
   if(month=4||month=6||month=9||month=11)
                                      ^
/in/foo.c:5:20: warning: variable 'day' set but not used [-Wunused-but-set-variable]
     int year,month,day;
                    ^~~