#include <iostream>
#include <bits/stdc++.h>
#include <string>
using namespace std;

string multiply(string num1, string num2){

    int len1 = num1.size();
    int len2 = num2.size();

    vector<int> result(len1 + len2, 0);

    int i_n1 = 0;
    int i_n2 = 0;

    for(int i=len1-1; i>=0; i--){

        int carry = 0;
        int n1 = num1[i] - '0';

        i_n2 = 0;

        for(int j=len2-1; j>=0; j--){
            int n2 = num2[j] - '0';

            int sum = n1*n2 + result[i_n1 + i_n2] + carry;

            carry = sum/10;
            result[i_n1 + i_n2] = sum % 10;

            i_n2++;
        }

        if (carry > 0)
            result[i_n1 + i_n2] += carry;

        i_n1++;

    }

    int i = result.size() - 1;
    while (i>=0 && result[i] == 0)
        i--;

    string str_result = "";

    while (i >= 0)
        str_result += std::to_string(result[i--]);

    return str_result;

}

int main()
{
    int a,b;

    cout<< "Podaj liczbe:"<<endl;
    cin>>a; //50
    b=a-1; //49
    string temp = to_string(a);
    while(b>=1){
    string str1=temp;
    string str2=to_string(b);

    temp=multiply(str1, str2);
    b--;
    }
    //tu wypisze tylko wynik
    cout<<temp;

//czesc kodu odpowiedzialna za wypisywanie od tylu po jednej cyfrze
   /* string result;
    int leng=temp.length();
    for(int i=leng-1; i>=0;i--){
            result = temp[i] + result;
        cout<<result<<endl;
    }
    */
    return 0;
}