#include <bits/stdc++.h>
using namespace std;
int main() {
  string s;
  getline(cin, s);
  int i, l, count = 0;
  l = s.length();
  sort(s.begin(), s.end());
  for (i = 0; i < l; i++) {
    if (s[i] >= 97 && s[i] <= 122) {
      count++;
      if (s[i] == s[i + 1]) {
        count--;
      }
    }
  }
  cout << count;
}
