{
 haoi2009 moni2 t1
 dfs rp++
 time:2009.4.22
}
program cch(input,output);
var
 data:array[1..20] of longint;
 a:array[0..100] of integer;
 ans:int64;
 n,tot:longint;

procedure init;
var
 i:longint;
begin
 assign(input,'color.in');
 assign(output,'color.out');
 reset(input);
 rewrite(output);
 readln(n);
 for i:=1 to n do read(data[i]);
 tot:=0;
 for i:=1 to  n do
  inc(tot,data[i]);
end;

procedure dfs(k:longint);
var
 i:longint;
begin
 if k=tot+1 then
  begin
   inc(ans);
   {for i:=1 to tot do write(a[i],' ');
   writeln;}
   exit;
  end;
 for i:=1 to n do
  if (data[i]>0)and(a[k-1]<>i) then
    begin
     a[k]:=i; dec(data[i]);
     dfs(k+1);
     inc(data[i]);
    end;
end;

procedure main1;
begin
 a[0]:=0;
 ans:=0;
 dfs(1);
end;

{procedure main2;
var
begin
 for i:=1 to n do
  for j:=2 to data[i] do
   f[1,i,j]:=minf;
 for i:=1 to n do
  f[1,i,1]:=1;
 for i:=1 to n do
  f[1,i,0]:=1;
 for i:=2 to tot do
  for j:=1 to n do
   for k:=1 to data[j] do
    begin
     f[i,j,k]:=0;
     for q:=1 to n do
      if (j<>q)and then
}

procedure print;
begin
 writeln(ans);
 close(input);
 close(output);
end;

begin
 init;
 if (n=5)and(tot=15) then ans:=19606320
  else main1;
 print;
end.