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

fstream fin("fact.in", ios::in);
fstream fout("fact.out", ios::out);

int main()
{
    int p; fin>>p;

    if(p == 0)
        fout<<1;
    else
    {
        long long unsigned int i = 1;

        for(long long unsigned int counter = 0; counter < p; i++)
        {
            counter++;
            if(i % 5 == 0)
                counter ++;
            //cout<<counter<<"\n";
        }

        fout<<(i - 1) * 5;
    }
}