#include <cstdlib>
#include <iostream>
#include <string>
#include <algorithm>
using namespace std;
string bin;
int duljina;
string b0,b1,b2,b3,b4,b5,b6,b7,b8,b9,ba,bb,bc,bd,be,bf;
int main(int argc, char *argv[])
{
    b0 = "0000";
    b1 = "0001";
    b2 = "0010";
    b3 = "0011";
    b4 = "0100";
    b5 = "0101";
    b6 = "0110";
    b7 = "0111";
    b8 = "1000";
    b9 = "1001";
    ba = "1010";
    bb = "1011";
    bc = "1100";
    bd = "1101";
    be = "1110";
    bf = "1111";

    cin >> bin;
    duljina = bin.length();
    if (duljina < 4){
    reverse(bin.begin(), bin.end());
    if (bin == "b0") cout << "0" << endl;
    else if (bin == "b1") cout << "1" << endl;
    else if (bin == "b2") cout << "2" << endl;
    else if (bin == "b3") cout << "3" << endl;
    else if (bin == "b4") cout << "4" << endl;
    else if (bin == "b5") cout << "5" << endl;
    else if (bin == "b6") cout << "6" << endl;
    else if (bin == "b7") cout << "7" << endl;
    else if (bin == "b8") cout << "8" << endl;
    else if (bin == "b9") cout << "9" << endl;
    else if (bin == "ba") cout << "a" << endl;
    else if (bin == "bb") cout << "b" << endl;
    else if (bin == "bc") cout << "c" << endl;
    else if (bin == "bd") cout << "d" << endl;
    else if (bin == "be") cout << "e" << endl;
    else if (bin == "bf") cout << "f" << endl;
}
    system("PAUSE");
    return EXIT_SUCCESS;
}