#include <bits/stdc++.h>
using namespace std;
int main() {
  string str;
  getline(cin, str);
  set<char> s;
  for (int i = 0; i < str.length(); i++) {
    if (!(str[i] == '{' || str[i] == ',' || str[i] == '}' || str[i] == ' ')) {
      s.insert(str[i]);
    }
  }
  int a = s.size();
  cout << a;
}
