#include <bits/stdc++.h>
int main() {
  int mem[26] = {0};
  char c;
  int cnt = 0;
  while ((c = getchar()) != '\n') {
    if (c >= 'a' && c <= 'z') {
      mem[c - 'a']++;
      if (mem[c - 'a'] == 1) cnt++;
    }
  }
  printf("%d", cnt);
}
