#include <bits/stdc++.h>
int main() {
  std::string input;
  getline(std::cin, input);
  std::set<char> letters;
  for (int k = 1; k < input.size(); k += 3) {
    if ('a' <= input[k] && input[k] <= 'z') {
      letters.insert(input[k]);
    }
  }
  printf("%ld\n", letters.size());
  return 0;
}
