#include <bits/stdc++.h>
using namespace std;
int main() {
  string s;
  getline(cin, s);
  int n = 0;
  char x = '1';
  for (int i = 0; i < s.length(); i++) {
    if (isalpha(s[i])) {
      n++;
      for (int j = i + 1; j < s.length(); j++) {
        if (s[i] == s[j]) {
          s[j] = x;
        }
      }
    }
  }
  cout << n;
  return 0;
}
