40-20= 50-20= 80-40= 80-50=
80-70= 90-10= 50-10= 50-20=
50-40= 90-40= 80-30= 40-20=
30-20= 80-30= 60-50= 30-20=
70-20= 90-60= 70-40= 50-30=
40-20= 50-20= 80-40= 80-50=
80-70= 90-10= 50-10= 50-20=
50-40= 90-40= 80-30= 40-20=
30-20= 80-30= 60-50= 30-20=
70-20= 90-60= 70-40= 50-30=