var fi,fo:text;
    p,x,rez:longint;
function calculate(n:longint):longint;
var i,ct:longint;
begin
  i:=5; ct:=0;
  while i<=n do
    begin
      ct:=ct + (n div i);
      i:=i*5;
    end;
  calculate:=ct;
end;
function binars(st,dr:longint):longint;
var mij,aux,aux2:longint;
begin
  while st<=dr do
    begin
      mij:=(st+dr)shr 1;
      aux:=calculate(mij);
      if aux=p then
        begin
          dr:=mij+1;
          aux2:=calculate(mij-1);
          if aux2<>p then
            begin
              binars:=mij;
              exit;
            end;
        end
      else
       if aux>p then dr:=mij+1
                else st:=mij-1;
    end;
  binars:=-1;
end;
begin
  assign(fi,'fact.in'); reset(fi);
  assign(fo,'fact.out'); rewrite(fo);
  read(fi,p);
  if p=0 then writeln(fo,1)
    else
     begin
       rez:=binars(0,2000000000);
       writeln(fo,rez);
     end;
  close(fi);
  close(fo);
end.