§ Birkhoff Von Neumann theorem

   r
s [B|C]
  --+---
  [0|D]

§ Proof 1 of BVN (Constructive)

[#0.4  0.3  0.3]
[0.5   #0.2 0.3]
[0.1   0.5  #0.4]
0.2 [1 0 0]    [0.2 0.3 0.3]
    [0 1 0] +  [0.5 0   0.3]
    [0 0 1]    [0.1 0.5 0.4]   
[0.2 0.3 0.3]    
[0.5 0   0.3]    
[0.1 0.5 0.4]    
[#0.2  0.3   0.3]    
[0.5   0    #0.3]    
[0.1  #0.5   0.4]    
   [1 0 0]   [0    0.3   0.3]
0.2[0 0 1] + [0.5  0     0.1] 
   [0 1 0]   [0.1  0.3   0.4]

§ Nice method to find permutation that makes progress