Problem Description

Eito-kun will start attending in-person classes at Kyoto University from the second semester.

Since the first semester was entirely online, Eito-kun is not familiar with the university's layout.

Therefore, he wants to estimate the time it takes to move between classrooms in advance.

You are given the coordinates of $ N $ classrooms. The coordinates of the $ i $-th classroom are $ (x_i, y_i) $.

Assuming you start at the $ 1 $-st classroom, calculate the total distance traveled when moving sequentially to the $ N $-th classroom.

The distance from coordinates $ (a, b) $ to coordinates $ (c, d) $ is given by $ |a - c| + |b - d| $.

Input Format

The input is given from the standard input in the following format:

$ N $ $ x_1 $ $ y_1 $ $ x_2 $ $ y_2 $ $\vdots$ $ x_N $ $ y_N $

Output Format

Output the total distance traveled from the $ 1 $-st classroom to the $ N $-th classroom in one line.

Sample Input and Output

Sample Input #1

3
1 2
2 3
4 6

Sample Output #1

7

Sample Input #2

1
0 0

Sample Output #2

0

Sample Input #3

4
-2 3
1 4
5 2
4 -2

Sample Output #3

15

Notes/Hints

Constraints

• $1 \leq N \leq 100$
• $-100 \leq x_i, y_i \leq 100$ $(1 \leq i \leq N)$
• All inputs are integers.

Sample Explanation 1

The distance between the $ 1 $-st and $ 2 $-nd classrooms is $ |1 - 2| + |2 - 3| = 2 $, and the distance between the $ 2 $-nd and $ 3 $-rd classrooms is $ |2 - 4| + |3 - 6| = 5 $. Therefore, the total distance traveled is $ 2 + 5 = 7 $.

Sample Explanation 2

Since there is only one classroom, no movement is necessary.

见题面 Input 部分

见题面 Output 部分