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

// 7.5, 7.6 feladatok megoldasai

long long factorial (long long n) {
    if (n==0) return 1;
    return n * factorial(n-1);
}

int stringToInt (string n) {
    if (n == "") return 0;
    return (stringToInt(n.substr(0, n.size() -1)) * 10) + n.back() - '0' ; 
}

int maximum(vector<int> v) {

}

int main () {
    cout<<factorial(13);
    cout<<endl<<stringToInt("7839");
}