#include <bits/stdc++.h>
char s[1000], s1[800];
int a[30];
int main() {
  int l, sum, i;
  while (gets(s)) {
    sum = 0;
    memset(a, 0, sizeof(a));
    l = strlen(s);
    for (i = 0; i < l; i++) {
      if (s[i] >= 'a' && s[i] <= 'z') {
        a[s[i] - 'a']++;
      }
    }
    for (i = 0; i < 26; i++) {
      if (a[i] != 0) {
        sum++;
      }
    }
    printf("%d\n", sum);
  }
}
