#include <fstream>

using namespace std;

int v[18]={0,5,25,125,625,3125,15625,78125,390625,1953125,9765625,48828125,244140725,1220703125};

int main()
{
    long long int p,n=-1,i,d,s,mij,rasp;
    ifstream fin ("fact.in");
    ofstream fout ("fact.out");
    fin>>p;
    if (p>=1)
    {
        s=1;
        d=p*5;
        while (s<=d)
        {
        mij=(d+s)/2;
            rasp=0;
            for(i=1;v[i]<=mij;i++)
                {
                    rasp+=mij/v[i];
                }
            if(rasp==p)
            {
                n=mij;
                d=mij-1;
            }
            else
            {
                if(rasp<p)
                {
                    s=mij+1;
                }
                else
                {
                    d=mij-1;
                }
            }
        }
        fout<<n;
    }
    else
    {
    fout<<"1";
    }
}