记录编号	79028	评测结果	AAAAAAAAAAA
题目名称	[USACO Feb08] 麻烦的聚餐	最终得分	100
用户昵称	毕之	是否通过	通过
代码语言	Pascal	运行时间	0.034 s
提交时间	2013-11-04 22:29:45	内存使用	0.28 MiB

var
  a,b:array[0..30000,1..3]of integer;
  x,i,j,k,n,jie:integer;
function min(a,b:integer):integer;
begin
  if a<=b then exit(a) else exit(b);
end;
begin
  assign(input,'egroup.in');reset(input);
  assign(output,'egroup.out');rewrite(output);
  readln(n);
  fillchar(a,sizeof(a),$7F);fillchar(b,sizeof(b),$7F);
  for i:=1 to 3 do
  begin
    a[0,i]:=0;b[0,i]:=0;
  end;
  for i:=1 to n do
  begin
    readln(x);
    for j:=1 to 3 do
    for k:=1 to j do
    begin
      if j=x then a[i,j]:=min(a[i-1,k],a[i,j])
      else a[i,j]:=min(a[i-1,k]+1,a[i,j]);
    end;
    for j:=1 to 3 do
    for k:=j to 3 do
    begin
      if j=x then b[i,j]:=min(b[i-1,k],b[i,j])
      else b[i,j]:=min(b[i-1,k]+1,b[i,j]);
    end;
  end;
  jie:=32767;
  for i:=1 to 3 do
  begin
    if a[n,i]<jie then jie:=a[n,i];
    if b[n,i]<jie then jie:=b[n,i];
  end;
  writeln(jie);
  close(input);close(output);
end.