31/32*32/33*33/34+34/35*35/36*36/37*37/38*38/39*39/40*40/41 =
= 2427 /1394
31/32*32/33*33/34 = 31/34
34/35*35/36*36/37*37/38*38/39*39/40*40/41 = 34/41
31/34 + 34/41 = (31*41 + 34*34)/34*41 = 2427 /1394
31/32*32/33*33/34+34/35*35/36*36/37*37/38*38/39*39/40*40/41 =
= 2427 /1394
31/32*32/33*33/34 = 31/34
34/35*35/36*36/37*37/38*38/39*39/40*40/41 = 34/41
31/34 + 34/41 = (31*41 + 34*34)/34*41 = 2427 /1394