// Programmieren 1, Praktikum 2, Aufgabe 5
// Sven Eisenhauer
// 06.11.2004
//
// file: prg1p2_5.cpp
//
// purpose: program to reads 2 integers from keyboard and finds all prime number twins
//          between them, like 3 and 5 or 17 and 19
//

#include <iostream>
using std::cin;
using std::cout;
using std::endl;

int main()
{
	int iNumberA, iNumberB;
	int iMin, iMax;
	int iIsPrime1=0;
	int iIsPrime2=0;
	int iPrime1=0;
	int iPrime2=0;
	int iToTest=0;

	cout << "Please enter 1st number: ";
	cin >> iNumberA;
	cout << "Please enter 2nd number: ";
	cin >> iNumberB;
	cout << endl;

	// first find out, which is the bigger value.
	iMax=iNumberA;
	iMin=iNumberB;

	if (iNumberB > iNumberA)
	{
	    iMax=iNumberB;
	    iMin=iNumberA;
	}
    // First loop: Get all numbers between the 2 entered
	for (int iOuterCounter=iMax-1;iOuterCounter>iMin;iOuterCounter--)
	{
		iIsPrime1=0;
		for (int iInnerCounter=iOuterCounter-1;iInnerCounter>1;iInnerCounter--)
		{
			if ( 0 == iOuterCounter%iInnerCounter)
			    iIsPrime1=1;  // actual number is NOT a prime
		}// end inner for routine
		if (0 == iIsPrime1)
		{
			iPrime1=iOuterCounter;
			// now test, if iPrime1 - 2 is a prime
			iIsPrime2 = 0;
			iToTest = iOuterCounter - 2;
			for (int iInnerCounter2=iToTest-1;iInnerCounter2>1;iInnerCounter2--)
			{
				if (0 == iToTest%iInnerCounter2)
				    iIsPrime2=1;
			}
			if (0 == iIsPrime2)
			    iPrime2=iToTest;

			if ((0 == iIsPrime1) && (0 == iIsPrime2) && (iPrime2 > iMin))
			    cout << iPrime1 << "\t" << iPrime2 << endl;
		}
		// if (iIsPrime1 && iIsPrime2)
		//        cout << iPrime1 << "\t" << iPrime2 << endl;
	}
//	system ("pause");

	return 0;
}// end main