#include <bits/stdc++.h>
using namespace std;
int main() {
  char a[1002];
  gets(a);
  long long frq[123] = {0};
  long long sum = 0;
  for (long long i = 0; a[i] != '\0'; i++) {
    if (a[i] >= 97 && a[i] <= 122) {
      frq[a[i]]++;
    }
  }
  for (long long i = 0; i < 123; i++) {
    if (frq[i] >= 1) {
      sum++;
    }
  }
  cout << sum;
}
