# Cant learn simple neuron network

My task is to learn a simple neural network with input size 1, hidden layer size 8, and output size 1 (a function $$f = {0->1,1->0,2->0,3->1}$$, but can learn the network to get satisfying result.

I am using an activation function, back propagation, and initial values in range (-1,1).

However, I can not get better results in supremum error norm than 0.5, never achieved under 0.5.

What did I do wrong? That is only 4 examples to learn, why is so hard to learn that natwork? 2 years ago I tried to learn XOR in similar way and also had same problem.