#include <iostream>
#include <fstream>
using namespace std;

ifstream f;
ofstream g;

long int q,z,k,p;

long int crut(long int m)
                {
                long int c=5,s=0;
                 while (c<=m)
                  {
                    s+=(m/c);
                    c*=5;
                         }
                  return s;
                }

void caut(long int a,long int b)
                {
                q=(a+b)/2;
                z=crut(q);
                if(z==p&&(crut(q-1)!=p))g<<q;
                else
                if(z==p&&(crut(q-1)==p))caut(a,q-1);
                if(a==b&&z!=p)g<<-1;
                else
                if(z>p)caut(a,q-1);
                else
                if(z<p)caut(q+1,b);

                }



main()
{

f.open("fact.in");
g.open("fact.out");

f>>p;

if(p==0)g<<1;
else caut(0,500000000);

g.close();
}