#include <bits/stdc++.h>
using namespace std;
const int N = 2e5 + 5;
int main() {
  char A[1000];
  long long int i;
  for (i = 0; i < 1000; i++) {
    cin >> A[i];
    if (A[i] == '}') break;
  }
  long long int a[26] = {0};
  for (long long int j = 0; j < i; j++) {
    a[A[j] - 97]++;
  }
  long long int c = 0;
  for (long long int i = 0; i < 26; i++) {
    if (a[i] > 0) c++;
  }
  cout << c << endl;
}
