#include <fstream>
using namespace std;
ifstream f("fact.in");
ofstream g("fact.out");
int n,k,u,m,z;
long long p,s;
int main()
{
    f>>k;
 p=1;
    u=2000000000;
    z=5;
    if(k==0)
      {

      g<<1;
      return 0;
      }

    while(p<=u){
        m=(u+p)/2;
        s=0;z=5;
    while(z<=m){
        s=s+m/z;
        z=z*5;
        }
        if(s==k){
            while(m%5!=0)
                m--;
             g<<m;
             break;
        }
        else
            if(s<k)
                p=m+1;
                else
                    u=m-1;

    }
    if(p>u)
       g<<-1;
    return 0;
}