Marisa has $n \times 2$ mushrooms and she wants to brew $n$ potion bottles, each using exactly 2 mushrooms. If the $i^{th}$ mushroom is paired with the $j^{th}$ mushroom, the resulting potion has a power of $A_{i,j}$. Marisa wants to find the combination of mushrooms that maximizes the total power of the $n$ potion bottles.
### Input
- The first line contains an integer $n$.
- The next $n \times 2$ lines, $i$-th line contains $n \times 2$ integers $A_{i, j}$. It is guaranteed that $A_{i,j}=A_{j,i}$.
### Output
- Print the maximum total power of $n$ potion bottles.
### Constraints
- $1 \le n \le 10$.
- $0 \le |A_{i,j}| \le 10^6$.
### Example
Input:
```
1
0 -2
-2 0
```
Output:
```
-2
```
