#include <iostream>
#include <fstream>
using namespace std;

int calcFact(int p)
{
    if(p==0)
        return 1;
    else if(p==-1)
        return -1;

    int n=0;

    int i=0;
    while(i<=p)
    {
        n+=5;
    }

    return n;
}

int main()
{
    ifstream fin("fact.in");
    ofstream fout("fact.out");

    int p;
    fin>>p;

    fout<<calcFact(p);

    return 0;
}