def highest_power(cells,size):
    """
    Return the coordinates of the top left corner of the 3x3 array of
    cells with the highest total power.
    """
    max_power = 0
    coords = (-1,-1)
    for x in range(300 - size - 1):
        for y in range(300 - size - 1):
            power = 0
            for i in range(x,x + size):
                for j in range(y,y + size):
                    power += cells[i][j]
            if power > max_power:
                coords = (x + 1,y + 1)
                max_power = power

    return [coords, max_power]