#!/usr/bin/env python3
#coding:utf-8

import math
import string
import random
import heapq
from sys import stdin
# import numpy as np
# from matplotlib import pyplot as plt
	

def main():
	read=stdin.readline

	#edit here!
	a=list(map(int,read().split()))
	a.sort()
	maxv=10000001
	l=0
	r=maxv
	while r-l>1:
		mid=(l+r)//2
		if a[-1]<mid:
			r=mid;
		elif a[-1]>=mid and a[1]<mid:
			num=(a[-1]-mid)//2
			if num >=mid-a[1]+mid-a[0]:
				l=mid
			else :
				r=mid
		else:
			num=(a[-1]-mid)//2+(a[1]-mid)//2
			if num>=mid-a[0]:
				l=mid;
			else:
				r=mid
	print(l)




if __name__ == '__main__':
	main()