function val=string2(t,x)
	 N=1000; %% # of masses
     c=59927000000;
	 val=zeros(2*N,1);
	 for i=2:N-1
	     val(i)=x(i+N);
	     val(i+N)=c*(x(i-1)-x(i)+x(i+1)-x(i));
     end
     val(1)=x(N+1);
     val(N)=x(2*N);
     val(N+1)=c*(-x(1)+x(2)-x(1));
     val(2*N)=c*(-x(N)+x(N-1)-x(N));
end
