Please help
Why am I getting floating-point invalid operation on test 3?
Would it be possible to see the test values?

program pr_1;
var n, i, x: longint;
a: real;
begin
read(n);
for i:=1 to n do
begin
  read(x);
  a:= (1 + sqrt(8*x-7))/2;
  if (Frac(a) = 0.0) then
    write('1 ')
  else
    write('0 ');
end;
end.