[Programmers] Lv0. 다음에 올 숫자

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;
    }
}