# 1
а b c 
3 4 1
3 4 2
3 4 3
3 4 4

# 2
a b
0 0
0 1
4 3

# 3
a b
1 1 2
1 2 0
1 2 1  (-1 instead -2)
1 2 1  (-4 instead -2)
2 3 1
1 2 0.000001