#!/usr/bin/ python3.8
import sys
read = sys.stdin.buffer.read
readline = sys.stdin.buffer.readline
readlines = sys.stdin.buffer.readlines


def yuki9000(stdin):
    print('Hello World!')


def yuki480(stdin):
    N = int(stdin[0])
    print(N * (N + 1) // 2)


def yuki9001(stdin):
    A, B = map(int, stdin[0].split())
    S = stdin[1].rstrip().decode()
    print(A, B)
    print(S)


def main():
    stdin = readlines()
    n = len(stdin)
    if n == 1:
        S = stdin[0].rstrip()
        if S.isdigit():
            yuki480(stdin)
        else:
            yuki9000(stdin)
    if n == 2:
        yuki9001(stdin)


main()