#include <bits/stdc++.h>
using namespace std;
int main() {
  string s;
  int out = 0;
  vector<int> v(26);
  getline(cin, s);
  for (int i = 0; i < s.size(); i++) {
    if (s[i] == ' ') continue;
    if (s[i] < 123 && s[i] > 96) {
      v[s[i] - 97] = 1;
    }
  }
  for (int i = 0; i < v.size(); i++) out += v[i];
  cout << out;
}
