.PS
boxht = 0.2
boxwid = 0.2
movewid = 0.05

box; move;
box; move;
box; move;
box; move;
box "7"; move;
box; move;

S: box invis wid 0.1 ht 0.3; move;
P: box; move;
box; move;
box "7"; move;
box; move;
box; move;
P5: box; move;
box; move;
box; move;
box; move;
box; move;

line from S.sw to S.ne;
line from S.ne right 2.5;

box at P5+(0, 0.3); move;
box; move;
box "7"; move;
box; move;
box; move;

P1: box at P-(0, 0.25); move;
box; move;
box; move;
box; move;
box; move;
box; move;

R1: box at P1-(0, 0.3); move;
box; move;
box; move;
box; move;
box; move;
box "7"; move;
box; move;

line from R1.nw+(0, 0.05) right 1.45;

P2: box at R1-(0, 0.25); move;
box; move;
P23: box; move;
box; move;
box; move;
box; move;
box; move;

line from P2.sw-(0, 0.05) right 1.7;

R2: box at P23-(0, 0.3); move;
box "7"; move;
box; move;
box; move;
box; move;
box; move;

P3: box at R2-(0, 0.25); move;
box "7"; move;
box; move;
box; move;
box; move;
box; move;

line from P3.sw-(0, 0.05) right 1.45;

R3: box at P3-(0, 0.3); move;
box; move;
box; move;
box; move;
box; move;
box; move;
box; move;

P4: box at R3-(0, 0.25); move;
box; move;
P43: box; move;
box; move;
box "7"; move;
box; move;
box; move;

line from P4.sw-(0, 0.05) right 1.7;

R4: box at P43-(0, 0.3); move;
box; move;
box; move;
box; move;
box; move;
box; move;

P5: box at R4-(0, 0.25); move;
box; move;
box; move;
box; move;
box; move;
P51: box; move;

line from P5.sw-(0, 0.05) right 1.45;

box invis "0" at P51-(0, 0.3);
.PE