运行错误，无论你输入啥都只输出一种情况，求解
#include<stdio.h>int main()
{
int iMonth=0,iDay=0;
printf("enter the month you want to know the days\n");
scanf("%d",&iMonth);
switch(iMonth)
{
case 1:
case 3:
case 5:
case 7:
case 8:
case 10:
case 12:
iDay=31;
break;
case 4:
case 6:
case 9:
case 11:
iDay=30;
break;
case 2:
iDay=28;
break;
default:
iDay=-1;
break;
}
if(iDay=-1)
{
printf("there is a error with you enter\n");
}
else
{
printf("2010.%d has %d days\n",iMonth,iDay);
}
return 0;
}
