写一个输入一个年份和月份，判断这个月有多少天的代码 c语言

#include <stdio.h>

int main() {
int year, month, days;
printf("请输入年份和月份：\n");
scanf("%d%d", &year, &month);
switch(month) {
case 1:
case 3:
case 5:
case 7:
case 8:
case 10:
case 12:
days = 31;
break;
case 4:
case 6:
case 9:
case 11:
days = 30;
break;
case 2:
if((year % 4 == 0 && year % 100 != 0) || year % 400 == 0) {
days = 29;
} else {
days = 28;
}
break;
default:
printf("输入的月份有误！\n");
return 0;
}
printf("%d年%d月有%d天。\n", year, month, days);
return 0;
}