#include <fstream>
using namespace std;
ifstream f("fact.in");
ofstream g("fact.out");
int n,q=500000000,p=1,m,ok=0,nr,pr;
int main()
{
    f>>n;
    if(n==0)
        g<<1<<'\n';
    else
    {
        while(p<q)
        {
            m=p+(q-p)/2;
            nr=0;
            pr=5;
            while(pr<m)
             nr=nr+m/pr, pr*=5;
            if(nr==n)
             p=m, q=m;
            else if(nr<n)
             p=m+1;
            else
             q=m-1;
        }
        m=p+(q-p)/2;
        nr=0;
        pr=5;
        while(m/pr)
            nr=nr+m/pr, pr*=5;
        if(nr==n)
            ok=m;
        else if(nr<n)
            p=m+1;
        else
            q=m-1;
        if(ok<5)
            g<<-1<<'\n';
        else
         g<<ok-ok%5;
    }
    return 0;
}