#include <bits/stdc++.h>
using namespace std;
int main() {
  string s;
  getline(cin, s);
  int i, len = s.length(), c = 0, f[27], x;
  memset(f, 0, sizeof(f));
  for (i = 1; i < len - 1; i = i + 3) {
    x = s[i] - 'a';
    if (f[x] > 0) {
      f[x]++;
    } else {
      c++;
      f[x]++;
    }
  }
  cout << c << endl;
  return 0;
}
