#include<bits/stdc++.h>
using namespace std;
int main(){
	int a,g,s;
	cin>>a;
	g=a%10; 
	s=a/10;
	g!=s;
	if(g>s){
		printf("%d",g);
	}if(g<s){
		printf("%d",s);
	}
}
/**************************************************************
	Problem: 1622
	User: sucongyi
	Language: C++
	Result: Accepted
	Time:7 ms
	Memory:2072 kb
****************************************************************/