//cal01.cpp



//This program determines the number of the 1st January

//of any year. Specificly the routine 

//                             int day1January(int year)



//(c)Jordi Binefa i Martínez

//                            on January 28th, 2000



#include <stdio.h>

#include <iostream.h>



int isLeapYear(int number){

        if(number > 1582){

                if(number%100){

                        if(number%4) return 0;

                        else return 1;

                }else

                        if((number/100)%4) return 0;

                        else return 1;

        }else return 0;

}



int numLeapYearsFrom98(int number){

	int year, counter = 0;



	if(number < 1998){

		for(year = number; year < 1998 ; year++)

			if(isLeapYear(year))

				counter--;

	}else

		for(year = number; year > 1998 ; year--)

			if(isLeapYear(year))

				counter++;

	return counter;

}



int incDay(int day){

	day++;

	if(day > 7) day = 1;

	return day;

}



int decDay(int day){

	day--;

	if(!day) day = 7;

	return day;

}



int day1January(int year){

	int day = 4, leapYears, normalYears, defaultYear = 1998, i;

	

	leapYears = numLeapYearsFrom98(year);



	if(year > defaultYear){ //request year > 1998

		normalYears = (year-defaultYear) - leapYears;

		for(i=0 ; i < normalYears ; i++)

			day = incDay(day);

		for(i=0 ; i < leapYears ; i++)

			day = incDay(incDay(day)); //in leap years it's increased two days

		if(isLeapYear(year)) //if the year is leap musn't to advance

			day = decDay(day);

	}else{ //request year <= 1998

		normalYears = (defaultYear - year) + leapYears;

		for(i=normalYears ; i > 0 ; i--)

			day = decDay(day);

		for(i=leapYears ; i < 0 ; i++)

			day = decDay(decDay(day)); //in leap years it's decreased two days

	}

	return day;

}



int askYear(){

	int number;



	cout << "\nTell me a year : ";

	cin >> number;

	cout << "\n\n";



	return number;

}



void main(){

	int year;



	while(year = askYear()) //You can get out writing 0

		if (year < 2001) //I do this to write "was" or "will"

			cout << "On day 1st January " << year << " was " << day1January(year) << "\n\n";

		else

			cout << "On day 1st January " << year << " will " << day1January(year) << "\n\n";

}