Lightweight Neural Network++ output

Hi,

I use Lightweight Neural Network++ library to train a neural network
on the exp(x) function.
so I want 3 layers, 1 input, 1 ouput and n neurons.
I made the trainig on -5<x<5 and I try to draw my approximation on
-10<x<10.
All seems ok when exp(x) < 1 but when exp(x)>1 my neural network
always output 1.

I decide to test with f(x) = x and all is ok when 0<f(x)<1 but when
f(x) < 0 (respectively f(x)>1) my approximation =0 (respectively 1)

First lines of my training files:

30
1
1
-3.57142857143 0.028116
6.66133814775E-16 1.000000
3 20.085537
-5 0.006738
-3.71428571429 0.024373
....

Can Someone help me?

Thanks.