import java.io.PrintStream;
import java.util.Arrays;
import java.util.Scanner;

/**
 * Solution to Average Character
 * 
 * @author vanb
 */
public class averagecharacter_vanb
{
    /** Input. */
    private static Scanner sc;
    
    /** Output. */
    private static PrintStream ps;
    
    /**
     * Do it!
     */
    private void doit()
    {
        char s[] = sc.nextLine().toCharArray();
        
        int sum = 0;
        for( char ch : s ) sum += ch;
        ps.println( (char)(sum/s.length));
    }
        
    /**
     * Main.
     * 
     * @param args unused
     * @throws Exception
     */
    public static void main( String[] args ) throws Exception
    {
        sc = new Scanner( System.in );
        ps = System.out;
        
        new averagecharacter_vanb().doit();
    }

}