#include <fstream>

using namespace std;
ifstream fin ("fact.in");
ofstream fout ("fact.out");


int P;
int p, nrz;
int st, dr, mid;
int main()
{
    fin>>P;
    st=1, dr=1000000000;
    while(st<=dr)
    {
        mid=(st+dr)/2;
        p=5, nrz=0;
        while(p<=mid)
        {
            nrz+=mid/p;
            p*=5;
        }
        if(nrz<P)
            st=mid+1;
        else
            dr=mid-1;
    }
        p=5, nrz=0;
        while(p<=st)
        {
            nrz+=st/p;
            p*=5;
        }
         if(nrz==P)
            fout<<st;
         else
            fout<<-1;



    return 0;

}