#include <bits/stdc++.h>
int main() {
  char c[1001];
  gets(c);
  int chuaxet[1001];
  for (int i = 0; i < strlen(c); i++) {
    if (c[i] >= 'a' && c[i] <= 'z')
      chuaxet[i] = 1;
    else
      chuaxet[i] = 0;
  }
  int count = 0;
  for (int i = 0; i < strlen(c); i++) {
    if (chuaxet[i] == 1) {
      for (int j = i; j < strlen(c); j++) {
        if (c[j] == c[i]) {
          chuaxet[j] = 0;
        }
      }
      count++;
    }
  }
  printf("%d", count);
  return 0;
}
