Handsel

Alice and Brown are brothers in a family and each receives pocket money in celebration of the coming year. They are very close and share the total amount of the money fifty-fifty. The pocket money each receives is a multiple of 1,000 yen.

Write a program to calculate each one’s share given the amount of money Alice and Brown received.

Input

The input is given in the following format.

a b

A line of data is given that contains two values of money: a (1000 ≤ a ≤ 50000) for Alice and b (1000 ≤ b ≤ 50000) for Brown.

Output

Output the amount of money each of Alice and Brown receive in a line.

Examples

Input

1000 3000

Output

2000

Input

5000 5000

Output

5000

Input

1000 2000

Output

1500

inputFormat

Input

The input is given in the following format.

a b

A line of data is given that contains two values of money: a (1000 ≤ a ≤ 50000) for Alice and b (1000 ≤ b ≤ 50000) for Brown.

outputFormat

Output

Output the amount of money each of Alice and Brown receive in a line.

Examples

Input

1000 3000

Output

2000

Input

5000 5000

Output

5000

Input

1000 2000

Output

1500

样例

5000 5000

5000