# include<iostream> # include<cstring> using namespace std; int main(){ char a[1001],d='0'; int n,c; cin>>a; c=strlen(a); for(int i=0;i<c;i++){ if(a[i]>='0'&&a[i]<='9'){ if(a[i]>d){ d=a[i]; } } } cout<<d; return 0; }