DRAWLINE(D1,B,S1,B,1),COLORWHITE;
M1:=INTPART(3*N/7);
A120:=REF(B,M1)=HHV(B,2*M1+1);
B120:=FILTER(A120,M1);
C321:=BACKSET(B120,M1+1);
D119:=FILTER(C321,M1);
R1:=BACKSET(ISLASTBAR,BARSLAST(D119)+1); S10:=R1 REF(R1,1);
DRAWLINE(D119,B,S10,B,1),COLORYELLOW;
M2:=INTPART(1*N/10);
A2:=REF(B,M2)=HHV(B,2*M2+1);
B2:=FILTER(A2,M2);
C2:=BACKSET(B2,M2+1);
D2:=FILTER(C2,M2);
R4:=BACKSET(ISLASTBAR,BARSLAST(D2)+1); S2:=R4 REF(R4,1);
DRAWLINE(D2,B,S2,B,1),COLORGREEN;