10-4

#include<iostream.h>

void main ()
{
	int adadMabna8,
		baghiyeRaghamHaa; // avval baraabar
		// baa adadMabna8, bad ragham be ragham
		// az aan bar midarim.
		// masalan agar adadMabna8 = 123,
		// baghye/raghamHaa = 123, badesh
		// = 12, badesh =1
	int adadMabna10=0, raghamYekan;
	int _8_tavan_i=1;
	int adadMabna8Bood = 1;

	cout << "Yek adad dar mabna 8 vared konid:";
	cin >> adadMabna8;
	baghiyeRaghamHaa = adadMabna8;

	// ragham be ragham joda konim
	// har ragham raa dar 8^i zarb konim
	// va baa adadMabna10 jam konim
	while (baghiyeRaghamHaa) {
		raghamYekan = baghiyeRaghamHaa % 10;
		if (raghamYekan > 7) {
			cout << "adad mabna 8 nist" << endl;
			adadMabna8Bood = 0;
			break;
		}
		baghiyeRaghamHaa /= 10;

		adadMabna10 += 
			_8_tavan_i * raghamYekan;

		_8_tavan_i *= 8;
	}

	if (adadMabna8Bood) {
		cout << adadMabna8 << " (mabna 8) = "
			<< adadMabna10 << " (mabna 10)"
			<< endl;
	}
}