#include <bits/stdc++.h>
using namespace std;
int main() {
  string s;
  int a[1000], u = 0;
  getline(cin, s);
  for (int i = 0; i < s.length(); i++) {
    a[i] = (int)s[i];
  }
  sort(a, a + s.length());
  for (int i = 0; i < s.length() + 1; i++) {
    if (a[i] >= 97 && a[i] <= 122) {
      if (a[i] != a[i + 1]) u = u + 1;
    }
  }
  cout << u;
  return 0;
}
