내 풀이

class Solution {
    public int solution(int[] common) {
        int answer = 0;
        if ((common[1] - common[0]) == (common[2] - common[1])){
            answer = common[common.length-1]+(common[1] - common[0]);
        }else{
            answer = common[common.length-1]*(common[1]/common[0]);
        }
        return answer;
    }
}