function rmx=traceback(trace,idex)
 %
%	Chen Tingliang
%   tingliangchen@163.com
%   splab hit China
%   2006.5

 m=size(trace,1);
 n=size(trace,2);
 i=m;
 j=idex;
 while i>2
      if trace(i,j)==0
          i=i-1;
      elseif trace(i,j)==1
          i=i-1;
          j=j-1;
      else
          j=j-1;
      end          
 end
 rmx=j-1;