def main():

    n = int(eval(input()))

    print((sum(i for i in range(1, n + 1))))





if __name__ == '__main__':

    main()



# 初項a，交差dの数列n個の和

def arithmetic_series(a, d, n):

    return n * (2 * a + (n - 1) * d) // 2





def main():

    n = int(eval(input()))

    print((arithmetic_series(1, 1, n)))





if __name__ == '__main__':

    main()

def main():
    n = int(eval(input()))
    print((sum(i for i in range(1, n + 1))))


if __name__ == "__main__":
    main()

# 初項a，交差dの数列n個の和
def arithmetic_series(a, d, n):
    return n * (2 * a + (n - 1) * d) // 2


def main():
    n = int(eval(input()))
    print((arithmetic_series(1, 1, n)))


if __name__ == "__main__":
    main()

+# 初項a，交差dの数列n個の和 +def arithmetic_series(a, d, n): +    return n * (2 * a + (n - 1) * d) // 2 + + -    print((sum(i for i in range(1, n + 1)))) +    print((arithmetic_series(1, 1, n)))