import sys


def input():
    return sys.stdin.readline().strip()


def main():
    input()
    (*c,) = map(int, input().split())

    if c[0] * c[-1] >= 0:
        print(max(abs(c[0]), abs(c[-1])) * 2)
    else:
        print((c[-1] - c[0]) * 2)


if __name__ == "__main__":
    main()