function A=zhanglm(B)
[m,n]=size(B);
w(1:1,1:m)=zeros(1:1,1:m);
for i=1:m
    C=B(1:m,i:i);
    [u,l,v]=find(C);
    j=1;
    h=numel(u);
    while ismember(u(j),w) 
        if j+1>h,break;end;
        j=j+1;
    end;
    w(1,i)=u(j);
    B(u(j)+1:m,i:i)=zeros(m-u(j),1);
    B(1:u(j)-1,i:i)=zeros(u(j)-1,1);
    
    times=i
end;
A=B;