function M=creat_m_xs(row,column,a,b)

row=fix(row);
column=fix(column);

M = ones(row,column);

for c = 1:column
    for r = 1:row
        
        if r == c
            M(r,c) = a;
        elseif ((r-c) == 1)||((r-c)==-1)
            M(r,c) = b;
        else
            M(r,c) = 0;
        end
        
    end
end
end