s=input()
k=0
m=0
result=""
a="0123456789ABCDEF"
for i in range(len(s)-1,-1,-1):
    m=m+int(s[i])*2**k
    k=k+1
    if k==4 or i==0:
        k=0
        result=a[m]+result
        m=0
print(result)