# include<iostream> # include<cstring> using namespace std; int main(){ string s,x; int a=0; cin>>s; a=s.size(); for(int i=0;i<a;i++){ if(s[i]>='0'&&s[i]<='9'){ x[i]=s[i]; } } char max=-2147483649; for(int i=0;i<a;i++){ if(x[i]>max){ max=x[i]; } } cout<<max; return 0; }