Codeforces Round #253 (Div. 2) A. Anton and Letters

#include <iostream>
#include <vector>
#include <algorithm>
#include <string>
#include <set>

using namespace std;

int main(){
    string str;
    getline(cin,str);
    set<char> a;
    for(int i= 1 ; i < str.length()-1; i+=3 ){
        a.insert(str[i]);
    }
    cout<<a.size()<<endl;
}