#include <bits/stdc++.h>
using namespace std;
const long double pi = acos(-1.0);
long long gcd(long long a, long long b) {
  if (b == 0) return a;
  return gcd(b, a % b);
}
bool checkprime(long long n) {
  long long i = 2;
  while (i * i <= n) {
    if (n % i == 0) return 0;
    i++;
  }
  return 1;
}
bool check(long long a[], long long n) {
  for (long long i = 0; i < n; ++i)
    if (a[i] != i + 1) return 1;
  return 0;
}
long long fact(long long n) {
  if (n == 0) return 1;
  return n * fact(n - 1);
}
long long sod(long long n) {
  long long sum = 0;
  while (n) {
    sum += n % 10;
    n /= 10;
  }
  return sum;
}
vector<long long> v;
long long bs(long long low, long long high, long long val) {
  long long mid = (low + high) / 2;
  if (low == high) return high;
  if (v[mid] >= val)
    return bs(low, mid, val);
  else
    return bs(mid + 1, high, val);
}
void lucky(long long n, long long cur, long long ct4, long long ct7,
           long long val) {
  if (n == cur) {
    if (ct4 == ct7) {
      v.push_back(val);
    }
    return;
  }
  lucky(n, cur + 1, ct4 + 1, ct7, val * 10 + 4);
  lucky(n, cur + 1, ct4, ct7 + 1, val * 10 + 7);
}
void DJ() {
  set<char> a;
  string s;
  getline(cin, s);
  for (long long i = 0; i < s.size(); ++i) {
    if ((s[i] - 'a') >= 0 && (s[i] - 'a') <= 25) a.insert(s[i]);
  }
  cout << (long long)a.size();
}
signed main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  long long t = 1;
  while (t--) DJ();
  return 0;
}
