4
- John C. Mitchell: 3
- André Scedrov: 2
- Andreas Blass: 1
- Paul Erdös: 0
Alternate paths:
- John C. Mitchell: 3
- Albert R. Meyer: 2
- Daniel J. Kleitman: 1
- Paul Erdös: 0
- John C. Mitchell: 3
- Richard Statman: 2
- Frank Harary: 1
- Paul Erdös: 0
- John C. Mitchell: 3
- Richard Statman: 2
- Michael E. Saks: 1
- Paul Erdös: 0
(source)