The lengths (in kilometers) of rivers on the South Island of New Zealand that flow to the Tasman Sea are listed below. Find the mode.

River	Length (km)
Hollyford	76
Cascade	64
Arawhata	68
Haast	64
Karangarua	37
Cook	32
Waiho	32
Whataroa	51
Wanganui	56
Waitaha	40
Hokitika	64
Waimea	48
Motueka	108
Takaka	72
Aorere	72
Heaphy	35
Karamea	80
Mokihinui	56
Buller	177
Grey	121
Taramakau	80
Arahura	56