import java.util.Scanner;
/* * 亦或校验算法 */
public class Checksum_XOR { 

@SuppressWarnings("resource")
public static void main(String[] args) {
// TODO Auto-generated method stub
while(true){
int i = 0,j = 0;
Scanner scanner = new Scanner(System.in);
String in = scanner.nextLine();
int len = in.length();
short inb[] = new short[len];
for(i=0;i<len;i++){
inb[i] = charToHex(in.charAt(i));   //将String里的每一个char转换为Hex
}
for(i =0;i<len;i++){    //将每两个Hex合并成一个byte
inb[j] = (byte) (((inb[i]<<4)&0x00f0)|((inb[i+1])&0x000f));
i++;
j++;
}
byte temp = 0x00; //校验值
for(i = 0;i<len/2;i++){ //异或
temp ^= inb[i];
}
System.out.printf("%x", temp);
}
}
static short charToHex(char x){ //将单个char转换为Hex
short result = 0;
switch(x){
case 'a':result=10;break;
case 'b':result=11;break;
case 'c':result=12;break;
case 'd':result=13;break;
case 'e':result=14;break;
case 'f':result=15;break;
case 'A':result=10;break;
case 'B':result=11;break;
case 'C':result=12;break;
case 'D':result=13;break;
case 'E':result=14;break;
case 'F':result=15;break;
default:result = (short) Character.getNumericValue(x);break;
}
return result;
}
}