#include<iostream> #include<cstdio> //scanf()\printf() #include<cstring> #include<cmath> //sqrt()\pow()\abs()\ceil()\floor()\max()\min() using namespace std; int main(){ char N[15],max='0'; cin>>N; int s1=strlen(N);; for(int i=0;i<s1;i++){ if(N[i]>max) max=N[i]; } cout<<max; return 0; }