function dxdt = complex1(t,x)

NN=50;
w=8;

for n=1:NN,
    V(n)=0;
end

for n=NN/2-1:NN/2+1,
    V(n)=1;
end


dxdt(1)=(w*i*(x(2)-2*x(1))-i*V(1)*x(1))';
for I=2:NN-1,
dxdt(I)=(w*i*(x(I+1)+x(I-1)-2*x(I))-i*V(I)*x(I))';
end
dxdt(NN)=(w*i*(x(NN-1)-2*x(NN))-i*V(NN)*x(NN))';

dxdt = dxdt';