#include<bits/stdc++.h>
using namespace std;
int main(){
	int a,b,c,d,z;
	cin>>a>>b>>c>>d;
	z=a<b?(b>c?(b>d?b:d):(c>d?c:d)):(a>c?(a>d?a:d):(c>d?c:d));
	cout<<z; 
	return 0;
}

/**************************************************************
	Problem: 1305
	User: tangkaixuan
	Language: C++
	Result: Accepted
	Time:12 ms
	Memory:2072 kb
****************************************************************/