A, B, S = map(int, input().split())
a = abs(S - A)
b = abs(S - B)
if a <= b:
    print(a + S)
else:
    if S == 1:
        print(a + S)
    elif A != 0:
        print(b + min(S-1, a) + A)
    else:
        print(b + S + 1)