#include<bits/stdc++.h>
using namespace std;
int main(){
	int n,g,s;
	cin>>n;
	g=n%10;
	s=n/10;
	int max=g;
	if (max<s){
		max=s;
	}
	printf("%d",max);
	return 0;
}
/**************************************************************
	Problem: 1622
	User: xiaojingxuan
	Language: C++
	Result: Accepted
	Time:8 ms
	Memory:2072 kb
****************************************************************/