#include <iostream.h>
#include <conio.h>
#include <apvector.h>
#include <windows.h>

void clrscr()
{
    system("CLS");
}

apvector <int> values(4);

int gcd(int m, int n)
{
    if(n==0)
    {
        return m;
    }
    if(n > m)
    {
        return gcd(n, m);
    }
    return gcd(m-n, n);
}

int hexToDec(int h)
{
    switch(h){
        case 102: return 15;
        case 101: return 14;
        case 100: return 13;
        case 99: return 12;
        case 98: return 11;
        case 97: return 10;
        default: return h-48;
    };
}

int hexToInt()
{
    return hexToDec(values[3])+hexToDec(values[2])*16+256*hexToDec(values[1])+4096*hexToDec(values[0]);
}

int getRelPrime()
{
    int num = 2;
    int toMatch = hexToInt();
    int val = gcd(num, toMatch);
    while(val != 1)
    {
        num++;
        val = gcd(num, toMatch);
    }
    return num;
}

int intToHex(int num)
{
    if(num > 9)
    {
        return 87+num;
    }
    return 48+num;
}

void putBiginHex(int num)
{
    values[0] = intToHex(num / 4096);
    num %= 4096;
    values[1] = intToHex(num / 256);
    num %= 256; 
    values[2] = intToHex(num / 16);
    num %= 16;
    values[3] = intToHex(num);
}

void increment(int val)
{
    if((val == 0) && (values[val] == 55))
    {
        values[val] = 48;
        return;
    }
    if(values[val] == 102)
    {
        values[val]=48;
        increment(val-1);
        return;
    }
    if(values[val] == 57)
    {
        values[val] = 97;
        return;
    }
    values[val]++;
}

void display()
{
    clrscr();
    cout<<char(values[0])<<char(values[1])<<char(values[2])<<char(values[3])<<endl;
}

void display(int i)
{
    clrscr();
    cout<<"Use the keys 1,2,3 and 4 to change the hexidecimal value on the display.]\n";
    cout<<"1 changes 0000 to 1000 and 3 changes 1f00 to 2000. Press the Enter key\n";
    cout<<"to change the display to a number relatively prime to the displayed number.\n";
    cout<<"To clear the display, press 0. To view these instructions, press i.\n";
    cout<<"Hit any key to return to the program";
}

void main()
{
    values[0]=values[1]=values[2]=values[3]=48;
    display(0);
    int texas = getch();
    while(texas != 27)
    {
        switch(texas){
                case 49: increment(0); break;
                case 50: increment(1); break;
                case 51: increment(2); break;
                case 52: increment(3); break;
                case 48: values[0]=values[1]=values[2]=values[3]=48; break;
                case 105: display(0); getch(); break;
                case 13: putBiginHex(getRelPrime()); break;
                default: break;
        };
        display();
        texas = getch();
    }
                
    /*cout<<"Enter a number: ";
    while((texas <= 1) || (texas > 32767)) //MAXINT
    {
        cin>>texas;
    }
    cout<<"The number "<<getRelPrime(texas)<<" is relatively prime to "<<texas<<endl;  */
    
}



/* esc = 27
   enter = 13
   0 = 48
   1 = 49
   2 = 50
   3 = 51
   4 = 52
   5 = 53
   6 = 54
   7 = 55
   8 = 56
   9 = 57 
   a = 97
   b = 98
   c = 99
   d = 100
   e = 101
   f = 102
   backspace = 8
*/