#include <iostream>
#include <cmath>
#include <iomanip>
using namespace std;

int main()
{
    start:
    int a, b, c;
    int op, select(0);
    while (select != -1)
    {
        cout<<"----------------------\n";
        cout<<"Number"<<setw(14)<<"Operation";
        cout<<"\n----------------------\n";
        cout<<"1"<<setw(20)<<"Addition\n"<<"2"<<setw(20)<<"Subtraction\n"<<"3"<<setw(20)<<"Multiplication\n"<<"4"<<setw(20)<<"Division\n"<<"5"<<setw(20)<<"Modulus\n"<<"6"<<setw(20)<<"Difference\n"<<"7"<<setw(20)<<"Exit Program\n";
        cout<<"Enter operation number: ";
        cin>>op;

        while ((op>7) || (op<1))
        {
              cout<<"Operation must be a number from 1 - 7\n";
              cout<<"Enter operation number: ";
              cin>>op;
        }


        if (op == 7)
        return 0;

        cout<<"Enter the first number: ";
        cin>>a;
        cout<<"\nEnter the second number: ";
        cin>>b;
        switch(op)
        {
                  case 1: c = a+b;
                          break;
                  case 2: while ((select<1)||(select>2))
                          {
                              cout<<"Press 1 for "<<a<< " - "<<b<<endl<<"Press 2 for "<<b<<" - "<<a<<endl;
                              cin>>select;
                              switch(select)
                              {
                                            case 1: c = a-b;
                                                    break;
                                            case 2: c = b-a;
                                                    break;
                                            default: cout<<"Number must be 1 or 2\n";
                              }
                          }
                          break;
                  case 3: c = a*b;
                          break;
                  case 4: while ((select<1)||(select>2))
                          {
                              cout<<"Press 1 for "<<a<< " / "<<b<<endl<<"Press 2 for "<<b<<" / "<<a<<endl;
                              cin>>select;
                              switch(select)
                              {
                                            case 1: c = a/b;
                                                    break;
                                            case 2: c = b/a;
                                                    break;
                                            default: cout<<"Number must be 1 or 2\n";
                              }
                          }
                          break;
                  case 5: while ((select<1)||(select>2))
                          {
                              cout<<"Press 1 for "<<a<< " % "<<b<<endl<<"Press 2 for "<<b<<" % "<<a<<endl;
                              cin>>select;
                              switch(select)
                              {
                                            case 1: c = a%b;
                                                    break;
                                            case 2: c = b%a;
                                                    break;
                                            default: cout<<"Number must be 1 or 2\n";
                              }
                          }
                          break;
                  case 6: c = abs(a-b);
                          break;
                  case 7: return 0;
                  default: cout<<"Must be a number from 1 to 7";
        }
    cout<<"The answer is: "<<c<<endl;
    }
    system("pause");
}