#include <bits/stdc++.h>
using namespace std;
int main() {
  string colc;
  getline(cin, colc);
  set<char> set1;
  for (int x = 0; x < colc.size(); x++)
    if (colc[x] >= 'a' && colc[x] <= 'z') set1.insert(colc[x]);
  cout << set1.size() << endl;
  return 0;
}
