#include <bits/stdc++.h>
using namespace std;
int main() {
  char a[1000], b[1000];
  int c = 0, k = 0, i;
  cin.getline(a, 1000);
  for (i = 0; a[i]; i++) {
    if (a[i] >= 'a' && a[i] <= 'z') {
      b[k] = a[i];
      k++;
    }
  }
  b[k] = '\0';
  sort(b, b + k);
  for (i = 0; b[i]; i++) {
    if (b[i] == b[i + 1])
      continue;
    else
      c++;
  }
  cout << c << endl;
  return 0;
}
