#include <fstream>

using namespace std;
ifstream cin ("fact.in");
ofstream cout ("fact.out");
int main()
{
    int p,l=1,r=10000005,x,cm,rez,m;
    bool ok=1;
    cin>>p;
    if(p==0)
    {
        cout<<1;
        return 0;
    }
    else{
        while(l<=r && ok)
        {
            m=(l+r)/2;
            x=0;
            cm=m;
            while(cm)
            {
                x+=cm;
                cm/=5;
            }
            if(x<p)
            {
                l=m+1;
            }
            else if(x>p)
            {
                r=m-1;
            }
            else{
                ok=0;
                rez=m*5;
            }
        }
    }
    if(ok)
        cout<<-1;
    else cout<<rez;


    return 0;
}