#include <fstream>
using namespace std;
int main() {
ifstream fin ("semipalindrom.in");
ofstream fout ("semipalindrom.out");
int n;
fin >> n;
int aux = n;
int nrcifre = 0;
while (aux) {
nrcifre++;
aux /= 10;
}
int div = 1;
for (int i = 0; i < nrcifre / 2; i++)
div *= 10;
int jumatatedreapta = n % div;
n /= div;
if (nrcifre % 2 == 1)
n /= 10;
int jumatatestanga = n;
if (jumatatedreapta == jumatatestanga) {
fout << jumatatedreapta;
} else {
int primacifra;
while (n > 9)
n /= 10;
primacifra = n;
fout << primacifra;
}
return 0;
}