#include <iostream>
#include <fstream>
using namespace std;
ifstream f("fact.in");
ofstream g("fact.out");
long long p,i,ci;
int main()
{
    f>>p;
    for (i=1;i<=9999999;i++)
    {
        ci=i;
        while (ci%5==0)
        {
           p--;
           ci=ci/5;
        }

        if(p==0)
        {break;}
    }
    g<<i;
    f.close();
    g.close();
    return 0;
}