Help!I use binary search to find the answer.
Please give me some test! Thanks
{my wrong mode here}
const
  maxn=1000;
  maxm=1000000;
var
  a1,n:longint;
  ta1:real;
  a:array[1..maxn]of extended;

  procedure init;
  begin
{    assign(input,'1066.in'); reset(input);}
    readln(n,ta1);
    a1:=round(ta1*maxm);
    a[1]:=a1;
  end;

  procedure search(first,last:longint);
  var
    cha1,cha2:real;
    h,h1,h2:longint;

  function solve(x:longint):boolean;
  var
    te,i,j:longint;
  begin
    i:=2; a[2]:=x; solve:=true;
    repeat
      inc(i);
      a[i]:=2*(a[i-1]+maxm)-a[i-2];
      if a[i]<0
        then begin
          solve:=false; exit;
        end;
    until a[i]>a[i-1];
    dec(I);
    if first=last
      then begin
        for j:=i+1 to n do
          a[j]:=2*(a[j-1]+maxm)-a[j-2];
        writeln((a[n]/maxm):0:2);
        halt;
      end;
  end;

  begin
    h:=(first+last) div 2;
    if solve(h)
      then search(first,h)
      else search(h+1,last);
  end;

begin
  init;
  search(0,a1);
end.