443A - Anton and Letters

#include <cmath>#include <cstdio>#include <cstdlib>#include <cstring>#include <iostream>#include <string>#include <vector>#include <queue>#include <algorithm>using namespace std;bool mark[30];int main() {    //freopen("aa.in", "r", stdin);    int cnt = 0;    char op;    memset(mark, false, sizeof(mark));    while(cin >> op) {        if(op == '{' || op == '}' || op == ',') continue;        if(!mark[op-'a']) {            mark[op-'a'] = true;            cnt++;        }    }    cout << cnt << endl;    return 0;}