#include <bits/stdc++.h>
using namespace std;
int main() {
  long long i, ans = 0;
  string s;
  getline(cin, s);
  long long c[26];
  memset(c, 0, sizeof(c));
  for (i = 0; i < s.length(); i++)
    if (s[i] != '{' and s[i] != '}' and s[i] != ',' and s[i] != ' ') {
      c[s[i] - 'a']++;
      if (c[s[i] - 'a'] == 1) ans++;
    }
  printf("%lld\n", ans);
}
