#include <iostream>
#include <unordered_set>
#include <string>
 
using namespace std;
 
int main() {
    string word;
    cin >> word;
 
    unordered_set<char> uniqueLetters;
 
    // Подсчитываем количество уникальных букв в слове
    for (char letter : word) {
        uniqueLetters.insert(letter);
    }
 
    // Выводим количество уникальных букв в слове
    cout << uniqueLetters.size() << endl;
 
    return 0;
}
 

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