A,B,S = map(int,input().split())
if A<=B<=S:
    if A>0:
        print(S-B+S-A+A)
    else:
        print(S-B+S-1+2)
elif B<=A<=S:
    print(S-A+S)
elif B<=S<=A:
    print(A)
elif S<=A<=B:
    print(A)
elif S<=B<=A:
    print(A)
else:
    if A>0:
        print(min(S-A+S,B-S+S))
    else:
        print(min(S+S,B-S+S-1+2))