#include <bits/stdc++.h>
using namespace std;
int main() {
  int A[26] = {0}, count = 0;
  string s;
  getline(cin, s);
  for (int i = 1; i < s.size(); i += 3) {
    A[int(s[i]) - 97] = 1;
  }
  for (int i = 0; i < 26; i++) {
    if (A[i] == 1) {
      count++;
    }
  }
  cout << count;
  return 0;
}
