#include<fstream>
using namespace std;
ifstream in("fact.in");
ofstream out("fact.out");

int nrzero(int a)
{
    int nr=0;
    while(a>=5)
    {
        nr=nr+a/5;
        a=a/5;
    }
    if(a==0) return 1;
    return nr;
}


int cautarebinara()
{
    int d=100000000/5,s=1,nz,m,p;
    in>>p;
    while(s<=d)
    {
        m=(s+d)/2;
        nz=nrzero(5*m);
        if(nz==p) break;
        if(nz!=p)
        {
            if(nz<p) s=m+1;
            else d=m-1;
        }
    }
    if(p==0) return 1;
    if(s>d) return -1;
    return 5*m;
}

int main()
{

        out<<cautarebinara();
}