#735. Matrix: Sum of the main diagonal
You are given a matrix of integers. **Sum of the main diagonal**.
### Input
The first line has n n, each of the next n lines has n integers (a square matrix).
### Output
The answer.
Examples
Input
4 4 -7 -6 -4 2 -3 3 -2 -6 -7 -7 5 -4 -2 8 -2 -2
Output
-1
Input
5 5 1 4 8 2 -5 -4 6 -9 -4 -2 3 -7 3 -2 -1 4 -1 -1 -5 9 6 6 8 -9 -6
Output
-1
💡 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.