#include <bits/stdc++.h>
using namespace std;
int main() {
  bool repeat = true;
  char a[1000];
  char x;
  int sum = 0;
  int size = 0;
  while (repeat == true) {
    cin >> x;
    if (x != '{' && x != ' ' && x != ',' && x != '}') {
      int proc = true;
      for (int i = 0; i < size; i++) {
        if (x == a[i]) proc = false;
      }
      if (proc == true) {
        a[size++] = x;
      }
    }
    if (x == '}') {
      repeat = false;
    }
  }
  cout << size;
  return 0;
}
