9-И-2 ex.7

# -*- coding: utf-8 -*-
"""
Created on Sat Nov 21 20:14:32 2020

@author: Sergey
"""

data=list(map(int, input().split()))
a=max(data)
b=min(data)
c=8*a+b
c1=8*b+a
s=0
for elem in data:
    s+= elem
if s==c:
    print(b)
else:
    print(a)