import math
import sys
def S(): return sys.stdin.readline().rstrip()
def I(): return int(sys.stdin.readline().rstrip())
def MI(): return map(int, sys.stdin.readline().rstrip().split())
def LI(): return list(map(int, sys.stdin.readline().rstrip().split()))
def LS(): return list(sys.stdin.readline().rstrip().split())

x, y, d = MI()

if x > y:
    x, y = y, x

if d <= x:
    print(d+1)
elif d <= y:
    print(x+1)
elif d <= x + y:
    print(x + y - d + 1)
else:
    print(0)