#446 cifmax3

#include <iostream>

using namespace std;
int n, a, b, c, maxim;

int main(){
    cin>>n;
    a = n%10;
    b = n/10%10;
    c = n/100%10;

    maxim = a;
    if (b > maxim)
        maxim = b;
    if (c > maxim)
        maxim = c;

    cout<<maxim;

    return 0;
}