#P4887. Initial Bet

Initial Bet

Initial Bet

题面翻译

有五个人在玩游戏 每个人一开始有 bb 个硬币 有一种操作是把一个硬币给另一个人 给你所有人经过若干次操作的硬币数 c[i]c[i]0c[i]1000\le c[i]\le 100)求正整数 bb,若无解输出 1-1

题目描述

There are five people playing a game called "Generosity". Each person gives some non-zero number of coins b b as an initial bet. After all players make their bets of b b coins, the following operation is repeated for several times: a coin is passed from one player to some other player.

Your task is to write a program that can, given the number of coins each player has at the end of the game, determine the size b b of the initial bet or find out that such outcome of the game cannot be obtained for any positive number of coins b b in the initial bet.

输入格式

There are five people playing a game called "Generosity". Each person gives some non-zero number of coins b b as an initial bet. After all players make their bets of b b coins, the following operation is repeated for several times: a coin is passed from one player to some other player.

Your task is to write a program that can, given the number of coins each player has at the end of the game, determine the size b b of the initial bet or find out that such outcome of the game cannot be obtained for any positive number of coins b b in the initial bet.

输出格式

Print the only line containing a single positive integer b b — the number of coins in the initial bet of each player. If there is no such value of b b , then print the only value "-1" (quotes for clarity).

样例 #1

样例输入 #1

2 5 4 0 4

样例输出 #1

3

样例 #2

样例输入 #2

4 5 9 2 1

样例输出 #2

-1

提示

In the first sample the following sequence of operations is possible:

  1. One coin is passed from the fourth player to the second player;
  2. One coin is passed from the fourth player to the fifth player;
  3. One coin is passed from the first player to the third player;
  4. One coin is passed from the fourth player to the second player.