#include <bits/stdc++.h>
using namespace std;
int main() {
  set<char> ch;
  int sum = 0;
  string str;
  getline(cin, str);
  for (int i = 0; i <= str.length(); i++) {
    if (str[i] != ',' && str[i] != ' ' && str[i] != '{' && str[i] != '}' &&
        str[i] != 0) {
      ch.insert(str[i]);
    }
  }
  for (auto it = ch.begin(); it != ch.end(); it++) sum++;
  cout << sum << endl;
  return 0;
}
