#include <bits/stdc++.h>
using namespace std;
int main() {
  char a[1005];
  gets(a);
  int check[28], s = 0;
  memset(check, 0, sizeof check);
  for (int i = 0; i < strlen(a); i++)
    if (isalpha(a[i])) check[a[i] - 'a' + 1] = 1;
  for (int i = 1; i < 27; i++) s += check[i];
  cout << s << endl;
}
