# The main function
def main():
    # Read user input
    need_red, need_green, need_blue = map(int, input().split())
    have_red, have_green, have_blue = map(int, input().split())
    avail_red_green, avail_green_blue = map(int, input().split())

    # Track how much to purchase
    to_buy = 0

    # Satisfy red first
    if need_red > have_red + avail_red_green:
        print(-1)
        return
    if need_red > have_red:
        to_buy += need_red - have_red
        avail_red_green -= need_red - have_red
    
    # Satisfy blue next
    if need_blue > have_blue + avail_green_blue:
        print(-1)
        return
    if need_blue > have_blue:
        to_buy += need_blue - have_blue
        avail_green_blue -= need_blue - have_blue
    
    # Satisfy green last
    if need_green > have_green + avail_red_green + avail_green_blue:
        print(-1)
        return
    if need_green > have_green:
        to_buy += need_green - have_green
        # We don't need to adjust because there are no more satisfaction checks
    
    # Print the result
    print(to_buy)


# Check if this is the main program
if __name__ == "__main__":
    main()