from PIL import Image

def main():
    img = Image.open("greyscale.png").convert("L")
    pixels = list(img.getdata())
    n = len(pixels)

    total = 0
    for i in range(n):
        pi = pixels[i]
        for j in range(i + 1, n):
            total += abs(pi - pixels[j])

    print(f"Pixels read: {n}")
    print(f"Sum of abs diffs over all pairs: {total}")

if __name__ == "__main__":
    main()