function B=addpoint(x,y,A)
B=zeros(size(A)+[1 1]);
B(1:end-1,1:end-1)=A;
[M,N]=size(B);
B(M,1)=x; B(M,2)=y;
for j=3:N
    B(M,j)=(B(M,j-1)-B(M-1,j-1))/(B(M,1)-B(M-j+2,1));
end
