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

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