[백준 알고리즘] Python 쉽게 푸는 문제 1292번

https://www.acmicpc.net/problem/1292

from functools import reduce


def main():
    A, B = map(int, input().split(" "))

    i: int = 1
    nums: list[int] = []
    while True:
        if len(nums) > B:
            break
        nums.extend([i]*i)
        i += 1

    result = reduce(lambda val, acc: acc + val, nums[A-1:B], 0)
    print(result)


if __name__ == "__main__":
    main()