Progalap04

#include <iostream>
#include <string>

using namespace std;
bool hasonlit(string a, string b, int hossz)
{
    bool ugyanaz;
    int i = 0;
    while(i < hossz && a[i] == b[i])
    {
        i = i + 1;
    }
    ugyanaz = ( i >= hossz);
    return ugyanaz;
}

int main()
{
    string DNS;
    cin >> DNS;
    int K = (DNS.size()/2);
    int N = (DNS.size());
    bool hasonlosag = false;
    string egyik;
    string masik;
    int i,j;

    while (K >= 2 && !hasonlosag)
    {
        i = 0;
        while (i < (N-K) && !hasonlosag)
        {
            egyik = DNS.substr(i,K);
            j = i + K;
            while (j < (N-K) && !hasonlosag)
            {
                masik = DNS.substr(j, K);
                hasonlosag = hasonlit(egyik, masik, K);
                j++;

            }

            i++;
        }

        K = K - 1;
    }


    if(j >= N-K && !hasonlosag)
    {
        cout << "" << endl;
    }
    else if(j < N-K && hasonlosag)
    {
        cout << masik << endl;
    }


    return 0;
}