import sys
if sys.platform =='ios':
	import clipboard
	a=clipboard.get()
	a = a.split('\n')
	text = '\n'.join(a)
	with open('input_file.txt','w') as f:
		f.write(text)
	sys.stdin = open('input_file.txt')
sys.setrecursionlimit(410000000)
stdin = sys.stdin 
ni = lambda: int(ns())
na = lambda: list(map(int, stdin.readline().split()))
ns = lambda: stdin.readline().strip()
nm = lambda: map(int,input().split())
na_1 = lambda: list(map(lambda x:int(x)*(-1), stdin.readline().split()))
na_2 = lambda: list(map(lambda x:int(x)-1, stdin.readline().split()))
rnage=range
rnge=range
rage = range
rnag=range

x,y,d = nm()

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