#include <iostream>
#include <fstream>
using namespace std;
long long n,nr=0,x,y;
int main()
{
    ifstream f("fact.in");
    ofstream g("fact.out");
    f>>n;
    x=n*5;
    while (nr!=n)
    {
        nr=0;
        for (int i=5;i<=x;i+=5)
        {
            y=i;
            while (y%5==0)
            {
                nr++;
                y=y/5;
            }
        }
        if (nr>n) x=x-5;
        else if (nr<n) x=x+5;
    }
    g<<x;
    return 0;
}