var ax,bx,cx,ay,by,cy,s:real;
begin
write('Nhap toa do diem 1: '); readln(ax,ay);
write('Nhap toa do diem 2: '); readln(bx,by);
write('Nhap toa do diem 3: '); readln(cx,cy);
s:=((bx - ax)*(cy-ay)-(cx-ax)*(by-ay))/2;
if s=0 then write('Ba diem A,B,C khong lap thanh mot tam giac')
else write('Ba diem A,B,C lap thanh mot tam giac');
readln;
end.