N = int(input())
L = [[int(l) for l in input().split()] for _ in range(N-1)]

A = 0
B = 0
for t in L:
    A += t[0]
    B += t[1]

ans = min(A, B)+1
for i in range(N-1):
    if L[i][0] == A and L[i][1] > 0:
        ans -= 1
        break
    if L[i][0] > 0 and L[i][1] == B:
        ans -= 1
        break
print(ans)