from PIL import Image


def twist_image(input_file_name, output_file_name):
    im = Image.open(input_file_name)
    pixels = im.load()
    x, y = im.size
    im2 = im.crop((0, 0, x / 2, y))
    x2, y2 = im2.size
    im3 = im.crop((x / 2, 0, x, y))
    x3, y3 = im3.size
    pixels2 = im2.load()
    pixels3 = im3.load()
    for i in range(x2):
        for j in range(y2):
            r, g, b = pixels3[i, j]
            pixels[i, j] = r, g, b
    for i in range(x):
        for j in range(y):
            if i >= x / 2:
                r, g, b = pixels2[i - x / 2, j]
                pixels[i, j] = r, g, b
    im.save(output_file_name)