function k=find_inside(z,V)
% k=find_inside(z,V) returns index of 
% all drifters inside V.

% make domain
v1=V(1);v2=V(2);v3=V(3);v4=V(4);
a=v1+i*v3;b=v2+i*v3;c=v2+i*v4;d=v1+i*v4;
w=[a; b; c; d];
% find drifters inside domain
zz=z(:,2)+i*z(:,3);
k=inside(zz,w);
