错误提示显示  illegal else without matching if

#include<stdio.h>
main()
{
    int ia,ib;
    scanf("%d",&ia,&ib);
    switch(ia,ib)
    {   
        case 1 :
        case 3 :
        case 5 :
        case 7 :
        case 8 :
        case 10 :
        case 12 :printf("31\n");break;
        case 4 :
        case 6 :
        case 9 :
        case 11 :printf("30\n");break;
        if((ia%4==0&&ia%100!=0)||(ia%400==0))
        {
            case 2 :printf("29\n");break;
            else
            printf("28\n");break;
        }
    }
}

[此贴子已经被作者于2018-4-15 19:35编辑过]