A, B, C = map(int, input().split())
if A > B > C or A < B < C:
    print(0)
else:
    ans1 = 0
    ans2 = abs(A - C)

    if A == C:
        C -= 1
        ans1 += 1
    if C > A:
        tmp = A
        A = C
        C = tmp

    if B >= A:
        ans1 += B - A + 1
        B = A - 1

    if B <= C:
        ans1 += C - B + 1
        C = B - 1

    print(min(ans1, ans2))