#include <stdio.h>

int date_to_day(int year, int month, int day) {
	if (month < 3) {
		month += 12;
		year -= 1;
	}

	return ((13*month+3)/5 + day + year + year/4 - year/100 + year/400) % 7;
}

int main() {
	int rc, year, month, day, nd;

	printf("Enter a day (yyyy-mm-dd): ");
	rc = scanf("%d-%d-%d", &year, &month, &day);
	if (rc != 3) {
		printf("Failed to parse date\n");
		return 1;
	}

	nd = date_to_day(year, month, day);

	switch (nd) {
		case 0:
			printf("Monday\n"); break;
		case 1:
			printf("Tuesday\n"); break;
		case 2:
			printf("Wednesday\n"); break;
		case 3:
			printf("Thursday\n"); break;
		case 4:
			printf("Friday\n"); break;
		case 5:
			printf("Saturday\n"); break;
		case 6:
			printf("Sunday\n"); break;
	}

	return 0;
}