题解 | #尼科彻斯定理#

n = int(input())
p = 1
for i in range(1, n + 1):
    p += (i - 1) * 2
c = p  # 记录起始值
for i in range(n):
    print(p, end='')
    if p != c + 2 * (n - 1):
        print('+', end='')
    p += 2