a, b, s = [int(x) for x in input().split()]

res = 0
a_s = abs(a - s)
b_s = abs(b - s)
if s == 1 or a_s <= b_s:
    res += a_s + s
else:
    res += b_s
    if a < s:
        res += s
        if a == 0:
            res += 1
    else:
        if a_s < s:
            res += a_s + a
        else:
            res += (s - 1) + a

print(res)