• 思路：等差数列，m的立方如果由m个数组成，那么这m个数的平均数=m²，最小数为m² - m + 1
while True:
    try:
        m = int(input())
        left = m ** 2 - m + 1
        print("+".join(map(str, [(left + 2*i) for i in range(m)])))
    except:
        break