시간 제한 메모리 제한 제출 정답 맞은 사람 정답 비율
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문제

상근이는 등차수열을 이루는 정수 4개를 골랐다. 이것은 상근이가 고른 수 4개를 정렬했을 때, 인접한 쌍의 차이가 일정하다는 것을 의미한다. 그 다음 이렇게 고른 숫자 4개를 노래로 만들어서 외우고 다닌다.

어느날, 상근이는 자신이 고른 4개 숫자 중 1개를 까먹었다. 

상근이가 고른 네 개의 숫자 중 세 개가 주어졌을 때, 네 번째 숫자를 구하는 프로그램을 작성하시오.

입력

첫째 줄에 상근이가 고른 네 개의 숫자 중 세 개가 주어진다. 이 숫자는 크기 순이 아닐 수도 있고, -100보다 크거나 같고, 100보다 작거나 같은 정수이다.

출력

첫째 줄에 네 번째 숫자를 출력한다. 정답이 여러 개일 경우에는 아무거나 출력하면 된다. 또한 정답이 존재하지 않는 경우는 입력으로 주어지지 않는다.

예제 입력 1

4 6 8

예제 출력 1

10
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