#743. Matrix: Sum of the border elements
You are given a matrix of integers. **Sum of the border elements**.
### Input
The first line has n m (the number of rows and columns), each of the next n lines has m integers.
### Output
The answer.
Examples
Input
5 2 7 -5 -1 -6 -7 -8 4 -3 1 2
Output
-16
Input
4 4 -3 3 -9 -8 -8 -2 1 5 -8 5 -2 3 0 4 0 2
Output
-19
💡 You can solve it with Python, JavaScript or blocks. Read the input line by line with input(). Don't print a question (like input("Number: ")). Print exactly what the output asks for, nothing more.