#include<stdio.h>
#include<conio.h>

enum month {Jan=1, Feb , Mar , Apr, May, June, July, Aug, Sep, Oct, Nov, Dec};
enum day {Sun=1, Mon, Tue, Wed, Thu, Fri, Sat};

/* function calculating and return the day of the week.
input: day in the week, month, day for checking.
output: day in the week after calculating.
*/
int day_of_the_week (int month, int day, int weekDay)
{
	int dayOfTheWeek = ((day + (weekDay-1))%7);
	return dayOfTheWeek;
}
/* the function checking the invalid inputs.
input: month, day and weekday.
output: it tells us that we have a mistake and we need to change it.
*/
int checkInput (int month, int day, int weekDay)
{
	int return_=0;

	while (month>12 || day>31 || weekDay>7 || month<1 || day<1 || weekDay<1)
	{
		printf("Invalid input, try again\n");
		printf("Enter month to check:\n");
		scanf("%d", &month);
		printf("Enter day to check:\n");
		scanf("%d", &day);
		printf("Enter the weekday of the 1st of the month:(1-sunday, 2-monday, etc)\n");
		scanf("%d", &weekDay);
	}

	while (day > 28 && month == 2)
	{
		printf("Invalid input, try again\n");
		printf("Enter month to check:\n");
		scanf("%d", &month);
		printf("Enter day to check:\n");
		scanf("%d", &day);
		printf("Enter the weekday of the 1st of the month:(1-sunday, 2-monday, etc)\n");
		scanf("%d", &weekDay);
	}

    while (day > 31 && (month == 12 || month == 1 || month == 3 || month == 5 || month == 7 || month == 8 || month == 10))
	{
		printf("Invalid input, try again\n");
		printf("Enter month to check:\n");
		scanf("%d", &month);
		printf("Enter day to check:\n");
		scanf("%d", &day);
		printf("Enter the weekday of the 1st of the month:(1-sunday, 2-monday, etc)\n");
		scanf("%d", &weekDay);
	}

	while (day > 30 && (month == 4 || month == 6 || month == 9 || month ==11 ))
	{
		printf("Invalid input, try again\n");
		printf("Enter month to check:\n");
		scanf("%d", &month);
		printf("Enter day to check:\n");
		scanf("%d", &day);
		printf("Enter the weekday of the 1st of the month:(1-sunday, 2-monday, etc)\n");
		scanf("%d", &weekDay);
	}

	printf("The %d.%d will be ", day,month);

	return_= day_of_the_week(month,day,weekDay);

	return return_;

}


int main(void)
{

	int month =0;
	int day =0;
	int weekDay =0;


	printf("Hello! Welcome to the day calculator!\n");
	printf("Enter month to check:\n");
	scanf("%d", &month);
	printf("Enter day to check:\n");
	scanf("%d", &day);
	printf("Enter the weekday of the 1st of the month:(1-sunday, 2-monday, etc)\n");
	scanf("%d", &weekDay);

	int retInput = checkInput( month,day, weekDay );

	if ( retInput == Sun )
	{
		printf("Sunday.\n");
	}

	else if ( retInput == Mon )
	{
		printf("Monday.\n");
	}

	else if ( retInput == Tue )
	{
		printf("Tuesday.\n");
	}
	else if ( retInput == Wed )
	{
		printf("Wednesday.\n");
	}
	else if ( retInput == Thu )
	{
		printf("Thursday.\n");
	}
	else if ( retInput == Fri)
	{
		printf("Friday.\n");
	}
	else if ( retInput == Sat )
	{
		printf("Saturday.\n");
	}

	getch();
	return(0);
}