function [y,count] = Lower(L,b)
n = size(b);
y(1:n,1) = b(1:n,1);
count = 0;
for j = 1:n-1
    for i = j+1:n
        count = count+2;
        y(i) = y(i) - L(i,j)*y(j);
    end
end