#include <fstream>using namespace std;
using namespace std;
ifstream fin("palindromsd.in");ofstream fout("palindromsd.out");


bool ePalindrom(int nr) {
if(nr < 10) return true;
int rasturnat = 0, numar = nr;
while(numar > 0) { rasturnat = rasturnat * 10 + numar % 10; numar = numar / 10;	}
if(rasturnat == nr) return true;	else return false;}
int main() {
int pal[1000], n = 0, nr;
while(fin >> nr) { if(ePalindrom(nr)) pal[n++] = nr;	}
for(int i = 0; i < n; i++) { if(i % 2 == 0) {  fout << pal[i / 2] << " "; } else { fout << pal[n - (i/2 + 1)] << " "; }	}
}