var n,m,s:integer;
    p:0..100000000;
    f,g:text;
begin
assign(f,'fact.in');
assign(g,'fact.out');
reset(f);
read(f,p);
n:=0;
rewrite(g);
while p>=1 do begin
      s:=0;
      n:=n+5;
      m:=n;
      while m mod 5=0 do begin
            s:=s+1;
            m:=m div 5;
      end;
      p:=p-s;
end;
if p=0 then write(g,n)
       else write(g,'-1');
close(f);
close(g);
end.