시간 제한메모리 제한제출정답맞힌 사람정답 비율
2 초 128 MB172694740.517%

문제

맑은 날 울릉도에서 태백산맥을 바라보면 수평선 위로 N개의 산봉우리가(1 ≤ N ≤ 100,000) 보인다.  다음은 N = 5인 경우의 예이다.

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각각의 산들은 높이가 밑변 길이의 2배인 이등변삼각형이다. 산은 밑변 꼭짓점의 정수 x좌표 두 개로 표현된다.

울릉도에서 바라본 산맥의 보이는 면적을 계산하여라.

입력

첫째 줄에 N이 입력된다. 둘째 줄부터 N+1번째 줄까지, 각각의 줄에는 산 하나를 표현하는 왼쪽 꼭짓점의 x좌표, 아래쪽 꼭짓점의 x좌표가 공백을 사이에 두고 입력된다. 입력으로 주어지는 x좌표는 32767보다 작거나 같은 자연수이다.

출력

첫째 줄에 산맥의 보이는 면적을 출력한다. 답은 부호 있는 32비트 정수 범위 안에 있다.

예제 입력 1

5
2 7
6 9
12 15
14 21
20 25

예제 출력 1

114
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