麻烦各位大神帮我看看出了什么问题

  if( year%4 == 0 && month > 2 )

    flag = 1;

    else

    flag = 0;

   switch( month ) 

{    

    case 1:sum=day+flag;break;

    case 2:sum=day+flag+31;break;

    case 3:sum=day+flag+59;break;

    case 4:sum=day+flag+89;break;

    case 5:sum=day+flag+120;break;

    case 6:sum=day+flag+150;break;

    case 7:sum=day+flag+181;break;

    case 8:sum=day+flag+211;break;

    case 9:sum=day+flag+242;break;

    case 10:sum=day+flag+272;break;

    case 11:sum=day+flag+303;break;

    case 12:sum=day+flag+333;break;

}

printf("%d年%d月%d日是该年的第%d天\n",year,month,day,sum);

return 0;

}