레벨 : 1언어 : swift인덴트가 많은듯 하다. 분리가 필요할듯
https://github.com/raywenderlich/swift-algorithm-club/tree/master/Stack
에라토스테네스의 체https://ko.wikipedia.org/wiki/에라토스테네스의\_체
https://ko.wikipedia.org/wiki/유클리드\_호제법?tableofcontents=1
https://programmers.co.kr/learn/courses/30/lessons/92334레벨 : level1언어 : swift
https://programmers.co.kr/learn/courses/30/lessons/77484레벨 : 1언어 : swift
https://programmers.co.kr/learn/courses/30/lessons/72410레벨1swift
https://programmers.co.kr/learn/courses/30/lessons/81301레벨1swift
https://programmers.co.kr/learn/courses/30/lessons/86051
https://programmers.co.kr/learn/courses/30/lessons/76501
https://programmers.co.kr/learn/courses/30/lessons/70128