C :

#include <stdio.h>
#include <math.h>
#include <stdlib.h>
#include <time.h>
int main()
{
   // freopen("in","r",stdin);
   // freopen("out","w",stdout);

	int year, month;

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



    }
  return 0;
}

C++ :

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