#include <fstream>
#include<cmath>
using namespace std;
ifstream f("factorial.in");
ofstream g("factorial.out");
int numar (long long n)
{
    int p=5,nr=0;
    while(p<=n)
    {
        nr=nr+n/p;
        p*=5;
    }
    return nr;
}
int main()
{
    long long sum=0,i=0,j=0,p,d,st=1,dr=1000000000,mij,k,sol;
    f>>k;
    while(st<=dr)
    {mij=(st+dr)/2;
        d=numar(mij);
        if(d>=k)
        { sol=mij;
           dr=mij-1;
        }
        else if(d<k)
        {
            st=mij+1;
        }
    }
     if(numar(sol)==k) g<<sol; else g<<-1;
    f.close();
    g.close();
    return 0;
}