Cod sursă (job #93013)

#include <iostream>
#include <fstream>

using namespace std;

const int Nmax = 5e5;

char str[Nmax];

int main()
{
    ifstream f("bart.in");
    ofstream gd("bart.out");

    f >> str;
    int N = 0;
    while( str[N++] );

    int g=1;

    for(int i=0;i<N-1;i++)
    {
        if(str[i]!=str[i%g])
        {
            g=i+1;
        }
    }

    for(int i = 0; i < g ; i++){
        gd << str[i];
    }
    gd << endl;

    return 0;
}