#include <bits/stdc++.h>
using namespace std;
int main(){
	int n,i,j;
	cin>>n;
	i=n%10;
	j=n/10;
	if(i>j){
		cout<<i;
	}else{
		cout<<j;
	}
}

/**************************************************************
	Problem: 1622
	User: hongjiaming
	Language: C++
	Result: Accepted
	Time:8 ms
	Memory:2072 kb
****************************************************************/