function [earn,ind]=knapsack(profit,weight,capa,bck)
// Copyright INRIA
[lhs,rhs]=argn(0)
if (rhs<3|rhs>4) then 
  error(39)
elseif (rhs==3) then 
  bck=-1;
end;
if (bck<0) then bck=-1;end;
n=size(profit,2);nn=size(weight,2);
// check profit weight capa
if ((n<>nn)|(n<2)) then
  error('Bad dimensions of input vectors')
end;
if ((max(profit) <= 0)|(max(weight) <= 0)|(max(capa) <= 0)) then
  error('Profits, weights and capacities must be positive')
end;
[s,k]=sort(floor(profit)./floor(weight));
[ss,kk]=sort(-k);
p=profit(k);w=weight(k);
np1=n+1;
m=size(capa,2);
[s1,k1]=sort(capa);
[s2,k2]=sort(k1);
kap=s1($:-1:1);
mn=m*n;mnp1=m*np1;
[xstar,vstar]=m6knapsk(n,m,np1,mn,mnp1,p,w,kap,bck);
earn=vstar;
if(vstar==-3) then print(%io(2),'A knapsack cannot contain any item');end;
if(vstar==-4) then print(%io(2),'An item cannot fit into any knapsack');end;
if(vstar==-5) then print(%io(2),'A knapsack contains all the items');end;
ind=xstar;
ij=find(xstar<>0);
ind=zeros(xstar);ind(ij)=k2(xstar(kk(ij)));
