#include <stdio.h>
#include <stdlib.h>

typedef struct tm_ymd_641_t
{
	int y;
	int m;
	int d;
} tm_ymd_641;

int leapyear(int year)
{
	return (((year % 4 == 0) && (year % 100 != 0) || (year % 400 == 0)) ? 1 : 0);
}

int eom(const tm_ymd_641 date)
{
	static const int daysinmonth[2][12] =
	{
		{31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31},
		{31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31}
	};
	return daysinmonth[leapyear(date.y)][date.m - 1];
}

int iseom(const tm_ymd_641 date)
{
	return date.d == eom(date) ? 1 : 0;
}

int isvaliddate(const tm_ymd_641 date)
{
	return 1 <= date.m && date.m <= 12 && 1 <= date.d && date.d <= eom(date) ? 1 : 0;
}

tm_ymd_641 parse_date(char date[])
{
	tm_ymd_641 ymd_date;

	ymd_date.d = atoi(&date[6]);
	date[6] = '\0';
	ymd_date.m = atoi(&date[4]);
	date[4] = '\0';
	ymd_date.y = atoi(date);

	return ymd_date;
}

int main(void)
{
	char date[9];
	tm_ymd_641 ymd;

	printf("YYYYMMDD:");
	scanf("%s", date);
	ymd = parse_date(date);
	if (!isvaliddate(ymd))
	{
		puts("Input date is invalid!");
		abort();
	}
	if (iseom(ymd))
	{
		if (ymd.m == 12)
		{
			ymd.y++;
			ymd.m = 1;
		}
		else
		{
			ymd.m++;
		}
		ymd.d = 1;
	}
	else
	{
		ymd.d++;
	}
	printf("Next day is %d/%d/%d\n", ymd.y, ymd.m, ymd.d);

	return 0;
}