#include<iostream>
#include<vector>
using namespace std;
vector<int> alphabetCount(32, 0);
vector<int> firstIncr(32, -1);
int main(){
  string str;
  cin >> str;
  int maxLength = 0, currentLength = 0;
  for(int i = previousIndex; str[i] != 0; i++){
    alphabetCount[str[i] - 'a']++;
    if(alphabetCount[str[i] - 'a'] == 1){
      firstIncr[str[i] - 'a'] = i;
      currentLength++;
    }
    if(alphabetCount[str[i] - 'a'] == 2 || i == str.size() - 1){
      if(currentLength > maxLength)
        maxLength = currentLength;
      currentLength = i - firstIncr[str[i] - 'a'];
      for(int k = 0; k < i; k++)
        alphabetCount[str[i] - 'a'] = 0;
      i = firstIncr[str[i] - 'a'] + 1;
    }
  }
  cout << maxLength;
}