这个月多少天？

#include <stdio.h>
int main(){
    int mouth year days;
    printf("请输入月份:");
    scanf("%d",&mouth);
    switch(mouth){
           case 1:
           case 3:
           case 5: 
           case 7:
           case 8:
           case 10:
           case 12:
              day = 31
              break;
            case 4:
            case 6:
            case 9:
            case 11:
                days = 30;
                break;
            case 2:
               printf("请输入年份：");
               scanf("%d",&year);
               if((year%4==0&&year%100!=0)&&(year%400!=0)){
                   days=29;
                   }else{
                         days=28;
                         }
           break;
      default:
             printf("没有这个日期哦");
             break;
             }
           
    }