Sum of the Anti-Diagonal
Add up the anti-diagonal cells of a square grid.
Input format
The first line has two integers R and C (with R = C, a square matrix). Each of the next R lines has C space-separated integers describing one row.
Output format
Print the sum of the anti-diagonal, which runs from the top-right corner to the bottom-left corner.
Constraints
- Values fit in a 64-bit signed integer
- Trailing whitespace and a trailing newline are ignored by the judge
Read from stdin, write to stdout. Sample cases below show the exact format.
Sample cases
Example 1
Input
3 3
1 2 3
4 5 6
7 8 9Expected output
15Example 2
Input
2 2
1 2
3 4Expected output
5