a, b, s = map(int, input().split())

aa = s - a
bb = s - b

c = 0
if aa == 0:
  print(s)
else:
  if abs(aa) <= abs(bb) or (b == 1 and bb == 0):
    c += abs(aa)
    c += s
    print(c)
  else:
    c += abs(bb)
    t = c
    c += abs(aa)
    c += a
    print(min(c, t + s + a - 1))