| V1| V2| V3| V4
--+---+---+---+---
V1| 0 | 1 | 0 | 0 
--+---+---+---+---
V2| 0 | 0 | 1 | 1 
--+---+---+---+---
V3| 0 | 0 | 0 | 0 
--+---+---+---+---
V4| 0 | 0 | 0 | 0