LCM - tester

//Need some help making this easier to use.

    bool NextP = true; //outer loop
    int Up = 1, N1 = 2, N2 = 1;
    unsigned long int Mul = 0, Dev = 0;
    int Fixer = 0;

    //LCM - Least Common Multiple

    while(NextP)
    {
        Up = 1;
        N1 = 0;
        N2 = 0;
        if(NextP)
        {
            printf("Enter both numbers below.... \n");
            printf("The first number must be larger than the second number\n");
            printf("Enter 0 for both numbers to exit. \n");
            cin >> N1 >> N2;
            cout << endl;

        }
        else
        {
            printf("Exiting Program! \n");
        }
        if(N1 != 0 && N2 != 0)
        {
            //LCM loops start
            if( (N1 > N2) )
            {
                do
                {
                    Mul = N2 * Up;
                    //cout << N1 << " * " << Up << " = " << Mul <<endl;
                    Dev = Mul / N1;
                    //printf(" %f / %f = %f \n",Mul,N2,Dev);

                    printf("Loop %d \n",(int)Up);
                    Up++;
                }
                while(!IsWholeNumberFloat(Mul, N1));
                Fixer = (int)Up - 1;
                printf("Whole Number After %d Loops\n\n", Fixer);
                if(IsWholeNumber(Mul, Fixer))
                {
                    //printf("These are the hole numbers");
                    cout << N2 << " * " << Up - 1 << " = " << Mul <<endl;
                    cout << Mul << " / " << N1 << " = " << Dev << endl;
                }
            }
            else if((N2 > N1))
            {
                do
                {
                    Mul = N1 * Up;
                    //cout << N1 << " * " << Up << " = " << Mul <<endl;
                    Dev = Mul / N2;
                    //printf(" %f / %f = %f \n",Mul,N2,Dev);

                    printf("Loop %d \n",(int)Up);
                    Up++;
                }
                while(!IsWholeNumberFloat(Mul, N2));
                Fixer = (int)Up - 1;
                printf("Whole Number After %d Loops\n\n", Fixer);
                if(IsWholeNumber(Mul, Fixer))
                {
                    //printf("These are the hole numbers");
                    cout << N1 << " * " << Up - 1 << " = " << Mul <<endl;
                    cout << Mul << " / " << N2 << " = " << Dev << endl;
                }
            }
            else
            {
                system("cls");
                cout << "Programming or Input Error of some kind!?!?!?" << endl;
                cout << "OR" << endl;
                cout << "I just didn't want to show the math for two of the same number!" << endl;
                cout << "OR" << endl;
                cout << "You needed a clearing of the screen?" << endl;
                cout << endl;
            }
            //LCM loops end

        }
        else if(N1 == 0 && N2 == 0)
        {
            NextP = false;
            printf("Exiting Program! \n");
        }
    }