#include <bits/stdc++.h>
using namespace std;
int main() {
  int count[26] = {0}, c = 0, i;
  string str;
  getline(cin, str);
  for (i = 1; i <= str.length() - 1; i++) {
    if (str[i] == '}' || str[i] == ',') count[str[i - 1] - 'a']++;
  }
  for (i = 0; i <= 25; i++)
    if (count[i] > 0) c++;
  printf("%d\n", c);
}
