pic3(conc.circ)

import geometry;

size(9cm,0);
defaultpen(fontsize(12pt));
dotfactor = 4;


for(real i = 0.1; i<=0.4; i+=0.1){
draw( circle(origin, i) );
}

dot(origin);
fill(box( (-1/2,-1/2), (1/2,1/2) ), lightblue+opacity(0.5));
draw(box( (-1/2,-1/2), (1/2,1/2) ), white);
draw(box( (-1,-1), (1,1) ));