#include <bits/stdc++.h>
using namespace std;
int main() {
  bool letters[30];
  memset(letters, false, sizeof(letters));
  string s;
  int counter = 0;
  getline(cin, s);
  for (int i = 1; i < s.size() - 1; i++) {
    if (s[i] != ',' || s[i] != ' ') {
      if (letters[s[i] - 97] == false) {
        ++counter;
        letters[s[i] - 97] = true;
      }
    }
  }
  cout << counter << endl;
}
