#include <iostream>
#include <cstring>
using namespace std;

int main() {
	string s;
	cin >> s;
	for(int j = 0; j < s.size(); j++) {
		int i = j + 1;
		while (i < s.size()) {
			if(s[j] == s[i] and i != j) s.erase(i,1);
			else i++;
		}
	}
	cout << s.size();
	return 0;
}