大一新生

#include <stdio.h>

int main() {
    int year,month;

    while(scanf("%4d %2d",&year,&month)!=EOF)
    {
        if (year%100!=0&&year%4==0)//闰年
        {
            switch (month) 
            {
                case 1:
                case 3:
                case 5:
                case 7:
                case 8:
                case 10:
                case 12:printf("31\n");
                break;
                case 2:printf("29\n");
                break;
                case 4:
                case 6:
                case 9:
                case 11:printf("30\n");
            }
        }
        else if (year%400==0)//闰年
        {
            switch (month) 
            {
                case 1:
                case 3:
                case 5:
                case 7:
                case 8:
                case 10:
                case 12:printf("31\n");
                break;
                case 2:printf("29\n");
                break;
                case 4:
                case 6:
                case 9:
                case 11:printf("30\n");
            }
        }
        else //非闰年
        {
            switch (month) 
            {
                case 1:
                case 3:
                case 5:
                case 7:
                case 8:
                case 10:
                case 12:printf("31\n");
                break;
                case 2:printf("28\n");
                break;
                case 4:
                case 6:
                case 9:
                case 11:printf("30\n");
            }
        }
    }
    return 0;
}