#include <bits/stdc++.h>
using namespace std;
int main() {
  string str;
  getline(cin, str);
  char str1[10001];
  if ((str[0] == '{') && (str[1] != '}')) {
    int k = 0;
    int x = 0;
    while (str[k] != '\0') {
      if (str[k] == '}') {
        break;
      }
      if ((97 <= str[k]) && (str[k] <= 122)) {
        str1[x] = str[k];
        x += 1;
      }
      k += 1;
    }
    str1[x + 1] = '\0';
    int y;
    int temp;
    for (k = 0; str1[k] != '\0'; k++) {
      for (y = k + 1; str1[y] != '\0'; y++) {
        if (str1[y] <= str1[k]) {
          temp = str1[y];
          str1[y] = str1[k];
          str1[k] = temp;
        }
      }
    }
    k = 1;
    int counter = 1;
    while (str1[k] != '\0') {
      if (str1[k] != str1[k - 1]) {
        counter += 1;
      }
      k += 1;
    }
    cout << counter;
  } else {
    cout << 0;
  }
  return 0;
}
