#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  int TESTS = 1;
  while (TESTS--) {
    string s;
    getline(cin, s);
    vector<char> v;
    for (long long int i = 0; i < (long long int)s.size(); i++) {
      if (s[i] >= 97 && s[i] <= 122) {
        v.push_back(s[i]);
      }
    }
    set<char> sc((v).begin(), (v).end());
    cout << (long long int)sc.size() << "\n";
  }
  return 0;
}
