#include <fstream>
using namespace std;
ifstream f("fact.in");
ofstream g("fact.out");
int n,P,P1,putere,nr;
int main()
{
    f>>P;
    for(n=5;;n+=5)
    {
        putere=5;nr=0;
        while(putere<=n)
        {
            nr=nr+n/putere;
            putere*=5;
        }
        if(P==nr){g<<n<<'\n';break;}
    }
    f.close();
    g.close();
    return 0;
}