function [L,U,x]=Doolittle(A,b)
[n,m]=siz
for i=1:n;
    U(1,i)=A(1,i);U(i,i)=1;
    L(i,1)=A(i,1)/U(1,1);
end
for k=2:n;
    for j=k:n;
        s=0;
        for r=1:k-1;
            s=s+L(k,r)*U(r,j);
        end
        U(k,j)=A(k,j)-s;
    end
    for i=k+1:n;
        s=0;
        for r=1:k-1;
            s=s+L(i,r)*U(r,k);
        end
        L(i,k)=(A(i,k)-s)/U(k,k);
    end
end
for i=1:n;
    y(i)=(b(i)-L(i,1:i-1)*b(1:i-1))/L(i,i);
end
for j=n:-1:1;
    x(j)=(y(j)-U(j,j+1:n)*y(j+1:n))/U(j,j);
end