#include <bits/stdc++.h>
using namespace std;
const long long INF = 1000000000000000000;
bool a['z'];
int main() {
  string s;
  getline(cin, s);
  if (s.size() <= 2) {
    cout << 0;
    return 0;
  }
  for (int i = 1; i <= (s.size() - 1); i++) {
    a[s[i]] = 1;
    i += 2;
  }
  int h = 0;
  for (char i = 'a'; i <= 'z'; i++)
    if (a[i]) h++;
  cout << h;
  return 0;
}
