输入年月，输出该月天数（C语言）

#include
int main()
{
	int year,month,days;
	printf("请输入年，月：");
	scanf("%d %d",&year,&month);
	if(month<1||month>13) 
	{
		printf("数据不合法！！n"); 
	}
	else
	{
		switch(month)
		{
			case 1:days=31;
			    break;
		    case 2:
		    	if(year%4==0&&year%100!=0||year%400==0)
		    	days=29;
		    	else
		    	days=28;
		    	break;
		    case 3:days=31;break;
		    case 4:days=30;break;
		    case 5:days=31;break;
		    case 6:days=30;break;
		    case 7:days=31;break;
		    case 8:days=31;break;
		    case 9:days=30;break;
		    case 10:days=31;break;
		    case 11:days=30;break;
		    case 12:days=31;break;
		}
		printf("%d年%d月有%d天n",year,month,days);
	}
	
	
	
	return 0;
 }