var f : text;
   p,n,k,i,x : longint;
begin
     assign(f,'fact.in'); reset(f);
     readln(f,p);
     close(f); p:=abs(p);
     if p mod 5=0 then k:=p+1-(p div 5)
     else k:=p-(p div 5);
     n:=k*5;
     x:=n; i:=0;
     while x>=5 do
           begin
                i:=i+x div 5;
                x:=x div 5;
           end;
     if i<>p then n:=-1;
     assign(f,'fact.out'); rewrite(f);
     write(f,n);
     close(f);
end.