Contest Duration: - (local time) (110 minutes) Back to Home
A - BBQ Easy /

Time Limit: 2 sec / Memory Limit: 256 MB

### 問題文

うまく串を組み合わせたとき、N 個の串焼きに刺すことのできる具材の個数の和の最大値はいくらになるでしょうか？

• 1≦N≦100
• 1≦L_i≦100
• L_i は整数である。

### 入力

N
L_1 L_2 ... L_{2N}


### 出力

N 個の串焼きに刺すことのできる具材の個数の和の最大値を出力せよ。

### 入力例 1

2
1 3 1 2


### 出力例 1

3


1 番目と 3 番目、2 番目と 4 番目の串を組にすると、それぞれの串焼きには 1 個、 2 個の具材を刺すことができ、合計 3 個の具材を刺すことができます。

### 入力例 2

5
100 1 2 3 14 15 58 58 58 29


### 出力例 2

135


Score : 200 points

### Problem Statement

Snuke is having a barbeque party.

At the party, he will make N servings of Skewer Meal.

Example of a serving of Skewer Meal

He has a stock of 2N skewers, all of which will be used in Skewer Meal. The length of the i-th skewer is L_i. Also, he has an infinite supply of ingredients.

To make a serving of Skewer Meal, he picks 2 skewers and threads ingredients onto those skewers. Let the length of the shorter skewer be x, then the serving can hold the maximum of x ingredients.

What is the maximum total number of ingredients that his N servings of Skewer Meal can hold, if he uses the skewers optimally?

### Constraints

• 1≦N≦100
• 1≦L_i≦100
• For each i, L_i is an integer.

### Input

The input is given from Standard Input in the following format:

N
L_1 L_2 ... L_{2N}


### Output

Print the maximum total number of ingredients that Snuke's N servings of Skewer Meal can hold.

### Sample Input 1

2
1 3 1 2


### Sample Output 1

3


If he makes a serving using the first and third skewers, and another using the second and fourth skewers, each serving will hold 1 and 2 ingredients, for the total of 3.

### Sample Input 2

5
100 1 2 3 14 15 58 58 58 29


### Sample Output 2

135