#include <bits/stdc++.h>
using namespace std;
int main() {
  int num[128] = {0}, sum = 0, ch;
  char test[1000];
  while ((ch = getchar()) != '\n') {
    if (isalpha(ch)) {
      num[ch]++;
    }
    if (num[ch] == 1) {
      sum++;
    }
  }
  cout << sum << endl;
  return 0;
}
