#include <bits/stdc++.h>
using namespace std;
void solve() {
  string line;
  getline(cin, line);
  set<char> s;
  if (line.size() > 2) {
    for (int i = 1; i < line.size(); i += 3) {
      s.insert(line[i]);
    }
  }
  printf("%d\n", (int)s.size());
}
int main() {
  solve();
  return 0;
}
