Untitled

#include <bits/stdc++.h>
using namespace std;
void backtrack(string str, vector<bool> used, int len, int &num) {
    if (len == str.size()) {
        num++;

        return;
    }

    for (int i = 0; i < str.size(); i++) {
        if (used[i] == true) continue;
        if (i > 0 && str[i] == str[i - 1] && used[i - 1] == false) continue;
        used[i] = true;
        backtrack(str, used, len + 1, num);
        used[i] = false;
    }
}

int main() {
    string str;
    cin >> str;
    sort(str.begin(), str.end());
    int num = 0;
    vector<bool> used(str.size(), false);
    backtrack(str, used, 0, num);
    cout << num;
    return 0;
}