I have two ACCEPTED solution that gives different results (difference greater than 1E-5) in approximately 7.5-8% points.
Is this normal? :)

If you have access:
"Correct" solution: http://acm.timus.ru/getsubmit.aspx/6557034.cpp
Wrong solution: http://acm.timus.ru/getsubmit.aspx/6554840.cpp

Here some of this points:

-5.4 -4.0
-0.0 -4.0
5.4 -4.0
-5.4 -2.8
-2.7 -2.8
-2.4 -2.8
-2.1 -2.8
-0.6 -2.8
0.6 -2.8
2.1 -2.8
2.4 -2.8
2.7 -2.8
5.4 -2.8
-2.7 -2.5
-0.6 -2.5
0.6 -2.5
2.7 -2.5
-2.7 -2.2
2.7 -2.2
-5.1 -1.9
-4.8 -1.9
-1.8 -1.9
-0.3 -1.9
0.3 -1.9
1.8 -1.9
4.8 -1.9
5.1 -1.9
-4.2 -0.7
-2.7 -0.7
2.7 -0.7
4.2 -0.7
-1.8 -0.4
1.8 -0.4
-1.8 -0.1
1.8 -0.1
-1.8 0.2
1.8 0.2
-4.2 0.5
-2.1 0.5
-1.8 0.5
1.8 0.5
2.1 0.5
4.2 0.5
-4.2 0.8
4.2 0.8
-4.2 1.7
4.2 1.7
-5.1 2.0
5.1 2.0
-2.7 2.3
2.7 2.3
-5.4 2.6
-2.7 2.6
-2.4 2.6
-0.6 2.6
0.6 2.6
2.4 2.6
2.7 2.6
5.4 2.6
-5.4 2.9
-2.7 2.9
-2.4 2.9
-2.1 2.9
-0.6 2.9
0.6 2.9
2.1 2.9
2.4 2.9
2.7 2.9
5.4 2.9