# include<iostream> # include<cstring> using namespace std; int main(){ char s1[100]; cin>>s1; int n=strlen(s1); char _max='0'; for(int i=0;i<n;i++){ if(s1[i]=='-') continue; if(s1[i]>_max) _max=s1[i]; } cout<<_max; return 0; }