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():
	N = int(input())
	A, B = 0, 0
	for i in range(N - 1):
		a, b = getlist()
		A += a; B += b

	ans = max(A, B) - abs(A - B) + 1
	print(ans)


if __name__ == '__main__':
	main()