#include <bits/stdc++.h>
using namespace std;
int main() {
  string s;
  set<char> l;
  getline(cin, s);
  int i = 0;
  while (s[i]) {
    if (isalpha(s[i])) l.insert(s[i]);
    i++;
  }
  cout << l.size() << endl;
}
