#include <iostream>
#include<bits/stdc++.h>
using namespace std;
 
int main() {
	// your code goes here
	string str;
	cin>>str;
	int max1=INT_MIN;
	for(int i=0;i<str.size();i++){
	       set<char>s;
		   int j=i+1;
		   s.insert(str[i]);
		    while(j<str.size()){
		    int size=s.size();
		    s.insert(str[j]);
		    if(s.size()==size){
		    	break;
		    }
		   	j++;
		   }
		   int si=s.size();
		  max1=max(max1,si);
	}
	cout<<max1<<" ";
	return 0;
}

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