#include<bits/stdc++.h>
using namespace std;
int main(){
	int x,a,b;
	cin>>x;
	a=x%10;
	b=x/10;
	if(a>b)cout<<a;
	else cout<<b;
	return 0;
}

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