#include <bits/stdc++.h>
using namespace std;
vector<bool> v(26, false);
int main() {
  char s[1001];
  int c = 0;
  gets(s);
  for (int i = 0; i < strlen(s); i++) {
    if (s[i] == '{' || s[i] == ',' || s[i] == '}' || s[i] == ' ') {
      continue;
    }
    if (v[s[i] - 97]) continue;
    v[s[i] - 97] = true;
  }
  for (int i = 0; i < v.size(); i++) {
    if (v[i]) c++;
  }
  cout << c << endl;
}
