题解 | 尼科彻斯定理

def func():

    n = int(input())

    l = int(1 + 2*(n-1)*n/2)

    for i in range(n):
        if i == n-1:
            print(l+i*2, end='')
        else:
            print(l+i*2, end='+')


if __name__ == "__main__":
    func()