program p1;
var fi,fo:text;
    p,n,m,s:longint;
BEGIN
 assign(fi,'fact.in'); reset(fi);
 assign(fo,'fact.out'); rewrite(fo);

  read(fi,p);

  if p=0 then write(fo,1) else begin
                                n:=p*4;
                                 repeat
                                  m:=5; s:=0;
                                  while m<=n do begin
                                                 inc(s,n div m);
                                                 m:=m*5;
                                                end;
                                  inc(n);
                                 until s>=p;
                                 if s=p then write(fo,n-1)
                                        else write(fo,'-1');
                               end;

 close(fi); close(fo);
END.