def main():
    N = int(input())
    A = [0] * N
    B = [0] * N
    for i in range(1,N):
        A[i], B[i] = map(int, input().split())
    
    sumA = sum(A)
    sumB = sum(B)

    if sumA == sumB:
        print(sumA + 1)
    else:
        print(abs(sumA - sumB))


if __name__ == "__main__":
    main()