import sys; input = sys.stdin.buffer.readline
sys.setrecursionlimit(10**7)
from collections import defaultdict
con = 10 ** 9 + 7; INF = float("inf")

def getlist():
	return list(map(int, input().split()))

#処理内容
def main():
	x, y, d = getlist()
	x, y = list(sorted([x, y]))
	if d <= x:
		print(d + 1)
	elif x <= d and d <= y:
		print(x + 1)
	elif d <= x + y:
		print(x + y + 1 - d)
	else:
		print(0)





if __name__ == '__main__':
	main()