u := 1cm;

beginfig(1)

pickup pencircle scaled 0.75pt;

for i := 0 upto 4:
	draw (-0.5u, i*u)--(4.5u, i*u) dashed evenly withcolor 0.5white;
	label.lft(decimal i, (-0.5u, i*u));
endfor;

for i := 0 upto 4:
	draw (i*u, -0.5u)--(i*u, 4.5u) dashed evenly withcolor 0.5white;
	label.bot(decimal i, (i * u, -0.5u));
endfor;

drawarrow (-0.5u, 0u)--(4.5u, 0u) withcolor 0.5white;
drawarrow (0u, -0.5u)--(0u, 4.5u) withcolor 0.5white;

label.bot(btex $x$ etex, (4.5u, 0u));
label.lft(btex $y$ etex, (0u, 4.5u));

pickup pencircle scaled 4pt;

drawdot(0.5u, 2.5u);
drawdot(0.5u, 3.5u);
drawdot(1.5u, 2.5u);
drawdot(1.5u, 3.5u);

pickup pencircle scaled 2pt;

draw (-0.5u, 3u)--(4.5u, 3u);
draw (1u, -0.5u)--(1u, 4.5u);

endfig;

end