function f = ift(t)

 n = length(t);
 half=n/2;

 j=half;
 y(1)=t(1) +0i;

 for k = 2:j
   y(k)=t(2*k-1) -t(2*k)*i;
 end
   y(j+1)=t(2) +0i;
   j=j+2;
 for k=j:n
   y(k)=t(2*(n-k)+3) +t(2*(n-k)+4)*i;
 end


 f=ifft(y);
 f=real(f) * (n/2);