5.10正确版

#include<stdio.h>int main(){    int n,y;    scanf("%d %d",&n,&y);    switch(y)    {        case 1:printf("31");break;        case 2:if(n%4==0&&n%100!=0||n%400==0)                    printf("29");               else                    printf("28");               break;        case 3:printf("31");break;        case 4:printf("30");break;        case 5:printf("31");break;        case 6:printf("30");break;        case 7:printf("31");break;        case 8:printf("31");break;        case 9:printf("30");break;        case 10:printf("31");break;        case 11:printf("30");break;        case 12:printf("31");break;        default:printf("输入错误");    }    return 0;}