bzoj1211

prufer码水题
（n-2)！/[(d1-1)!*(d2-1)!*…*(dn-1)!]

var c:array[0..200] of longint;
    x,n,i,j,s:longint;
    ans:int64;

begin
  readln(n);
  if n=1 then
  begin
    readln(x);
    if x=1 then writeln(0)
    else writeln(1);
    halt;
  end;
  for i:=1 to n do
  begin
    read(x);
    if (x<1) or (x>n) then
    begin
      writeln(0);
      halt;
    end;
    for j:=2 to x-1 do
      inc(c[j]);
    s:=s+x-1;
  end;
  if s<>n-2 then
  begin
    writeln(0);
    halt;
  end;
  ans:=1;
  for i:=2 to n-2 do
  begin
    ans:=ans*int64(i);
    for j:=2 to n do
    begin
      while (c[j]>0) and (ans mod j=0) do
      begin
        dec(c[j]);
        ans:=ans div j;
      end;
    end;
  end;
  writeln(ans);
end.