c s t a r t with a comment
p qubo 0 4 4 6
c diagonals follow
0 0 3.4
1 1 4.5
2 2 2.1
3 3 -2.4
c elements follow
0 1 2.2
0 2 -3.4
1 2 4.5
c any comment you want
0 3 -3.2
1 3 4.5678
2 3 1