import torch
import torch.nn as nn
import torch.nn.functional as F

class HighwayNetwork(nn.Module):
    def __init__(self, size):
        super().__init__()
        self.W1 = nn.Linear(size, size)
        self.W2 = nn.Linear(size, size)
        self.W1.bias.data.fill_(0.)

    def forward(self, x):
        x1 = self.W1(x)
        x2 = self.W2(x)
        g = torch.sigmoid(x2)
        y = g * F.relu(x1) + (1. - g) * x
        return y