Here is my code. Can't understand my mistake.
var i,n,k:word;
    m:real;
begin
  readln(n);
  for i:=1 to n do
   begin
     readln(k);
     m:=(sqrt(8*k-7)-1)/2;
     if (frac(m))=0.0 then write('1 ')
                      else write('0 ');
   end;
   readln;
end.

So did I.
But I am AC now.
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program  p1196;
var
  i,n:longint;
  a,b:qword;        //point
begin
  readln(n);
  for i:=1 to n do
    begin
      readln(a);
      b:=trunc(sqrt((a-1)*2));
      if (a-1)*2=b*(b+1)
        then write(1,' ')
        else write(0,' ');
    end;
end.