#include <bits/stdc++.h>
using namespace std;
string n;
int ar[123], sum = 0;
int main() {
  getline(cin, n);
  for (int i = 1; i < n.size(); i += 3) {
    ar[(int)n[i]] = 1;
  }
  for (int i = 0; i < 123; i++) {
    sum += ar[i];
  }
  cout << sum;
  return 0;
}
