CF653A.Bear and Three Balls

Limak is a little polar bear. He has n balls, the i-th ball has size t__i.

Limak wants to give one ball to each of his three friends. Giving gifts isn't easy — there are two rules Limak must obey to make friends happy:

• No two friends can get balls of the same size.
• No two friends can get balls of sizes that differ by more than 2.

For example, Limak can choose balls with sizes 4, 5 and 3, or balls with sizes 90, 91 and 92. But he can't choose balls with sizes 5, 5 and 6 (two friends would get balls of the same size), and he can't choose balls with sizes 30, 31 and 33 (because sizes 30 and 33 differ by more than 2).

Your task is to check whether Limak can choose three balls that satisfy conditions above.

Limak 是一只小北极熊。他有 $n$ 个球，其中第 $i$ 个球的大小为 $t_i$。

Limak 想要给他的三位朋友每人一个球。送礼并不简单——Limak 必须遵守以下两条规则，才能让朋友们开心：

• 任意两位朋友不能得到相同大小的球；
• 任意两位朋友得到的球的大小之差不能超过 $2$。

例如，Limak 可以选择大小为 $4$、$5$ 和 $3$ 的球，或者大小为 $90$、$91$ 和 $92$ 的球。但他不能选择大小为 $5$、$5$ 和 $6$ 的球（因为有两位朋友会得到相同大小的球），也不能选择大小为 $30$、$31$ 和 $33$ 的球（因为 $30$ 和 $33$ 的差超过了 $2$）。

你的任务是判断 Limak 是否能选出三个满足上述条件的球。

The first line of the input contains one integer n (3 ≤ n ≤ 50) — the number of balls Limak has.

The second line contains n integers _t_1, _t_2, ..., t__n (1 ≤ t__i ≤ 1000) where t__i denotes the size of the i-th ball.

输入的第一行包含一个整数 $n$（$3 \leq n \leq 50$）—— 表示 Limak 拥有的球的数量。

第二行包含 $n$ 个整数 $t_1, t_2, \ldots, t_n$（$1 \leq t_i \leq 1000$），其中 $t_i$ 表示第 $i$ 个球的大小。

Print "YES" (without quotes) if Limak can choose three balls of distinct sizes, such that any two of them differ by no more than 2. Otherwise, print "NO" (without quotes).

如果 Limak 能够选择三个尺寸互不相同的球，使得其中任意两个球的尺寸之差都不超过 2，则输出 "YES"（不带引号）；否则输出 "NO"（不带引号）。

In the first sample, there are 4 balls and Limak is able to choose three of them to satisfy the rules. He must must choose balls with sizes 18, 16 and 17.

In the second sample, there is no way to give gifts to three friends without breaking the rules.

In the third sample, there is even more than one way to choose balls:

1. Choose balls with sizes 3, 4 and 5.
2. Choose balls with sizes 972, 970, 971.

在第一个样例中，共有 4 个球，Limak 能够从中选出 3 个球以满足规则。他必须选择尺寸分别为 $18$、$16$ 和 $17$ 的球。

在第二个样例中，不存在一种方式能将礼物分给三位朋友且不违反规则。

在第三个样例中，存在多种选择球的方式：

1. 选择尺寸分别为 $3$、$4$ 和 $5$ 的球。
2. 选择尺寸分别为 $972$、$970$ 和 $971$ 的球。