Comparing multiple char arrays in C++

I'm creating a program which consists of comparing three character arrays, the code is this:

#include <iostream>
#include <string.h>

using namespace std;

#define MAX 20

int main()
{
    char c1[MAX], c2[MAX], c3[MAX];

    cout << "Introduce array 1: ";
    cin >> c1;
    cout << "Introduce array 2: ";
    cin >> c2;
    cout << "Introduce array 3: ";
    cin >> c3;

    if (strcmp(c1, c2)==0 && strcmp(c1, c3) == 0)
    {
        cout << "The three arrays are equal" << endl;
    }
    else
    {
        if (strcmp(c1, c2) != 0 && strcmp(c1, c3) != 0)
        {
            cout << "The three arrays are different" << endl;
        }
        else
        {
            if (strcmp(c1, c2) == 0 && strcmp(c1, c3) != 0)
            {
                cout << "1 and 2 are equal" << endl;
            }
            else
            {
                if (strcmp(c1, c2) != 0 && strcmp(c1, c3) == 0)
                {
                    cout << "1 and 3 are equal" << endl;
                }
                else
                {
                    if ((strcmp(c1, c2) != 0) && (strcmp(c2, c3) == 0))
                    {
                        cout << "2 and 3 are equal" << endl;
                    }
                }
            }
        }
    }

    return 0;
}

The thing is that I don't know why when c2 and c3 are equal and c1 is different it tells me they're all different, in all the other cases it works fine, but I don't know what am I doing wrong.

Always comparing two pairs duplicates the effort – and you don't cover all possible pairs. Better:

if c1 == c2:
    if c2 == c3:
        all equal
    else:
        c3 differs from c1 and c2
else:
    // now c1 and c2 differ in any case!
    if c1 == c3:
        c2 differs from c1 and c3
    else:
        // c1 and c2 differ, c1 and c3 differ
        // but c2 and c3 could still be equal
        if c2 == c3:
            c1 differs from c2 and c3
        else:
            all three differ from one another