β原子

<p class="p0" style="text-indent:21.0000pt;text-align:justify;vertical-align:;"> <span style="font-size:11.0000pt;font-family:'微软雅黑';">在ACM的世界里有一种非常不稳定的原子，叫做</span><span style="font-size:11.0000pt;font-family:'微软雅黑';">β原子，这种原子的贮存有很多限制，他们必须横向排列在一个专用的管道内，每一个β原子都有左右两个相邻的β原子（头尾除外），β原子有一种属性叫做震荡值，两个相同震荡值的β原子相邻的话，这两个β原子就会相互碰撞，最后两个β原子都会湮灭。起初所有的β原子处于沉睡状态，当你通电后，他们就处于活跃状态，和相邻的原子发生反应。你的任务就是，看看这一排β原子在经过有限次相邻原子交换后是否可以通电（通电后他就会和周围相同震荡值的原子发生反应，我们为了避免反应，就不会通电）</span><span style="font-size:11.0000pt;font-family:'微软雅黑';"></span> </p>

<p class="p0" style="text-indent:21.0000pt;text-align:justify;vertical-align:;"> <span style="font-size:11.0000pt;font-family:'微软雅黑';">&nbsp;第一行一个整数N，代表接下来有N（1&nbsp;</span><span style="font-size:11.0000pt;font-family:'Arial';">≤</span><span style="font-size:11.0000pt;font-family:'微软雅黑';">&nbsp;N&nbsp;</span><span style="font-size:11.0000pt;font-family:'Arial';">≤</span><span style="font-size:11.0000pt;font-family:'微软雅黑';">&nbsp;100</span><span style="font-size:11.0000pt;font-family:'微软雅黑';">）个</span><span style="font-size:11.0000pt;font-family:'微软雅黑';">β原子</span><span style="font-size:11.0000pt;font-family:'微软雅黑';"></span> </p> <p class="p0" style="text-indent:21.0000pt;text-align:justify;vertical-align:;"> <span style="font-size:11.0000pt;font-family:'微软雅黑';">&nbsp;第二行N个整数（a</span><span style="font-size:11.0000pt;font-family:'微软雅黑';vertical-align:sub;">1</span><span style="font-size:11.0000pt;font-family:'微软雅黑';">,&nbsp;a</span><span style="font-size:11.0000pt;font-family:'微软雅黑';vertical-align:sub;">2</span><span style="font-size:11.0000pt;font-family:'微软雅黑';">,&nbsp;a</span><span style="font-size:11.0000pt;font-family:'微软雅黑';vertical-align:sub;">3</span><span style="font-size:11.0000pt;font-family:'微软雅黑';">,&nbsp;.........a</span><span style="font-size:11.0000pt;font-family:'微软雅黑';vertical-align:sub;">n</span><span style="font-size:11.0000pt;font-family:'微软雅黑';">)表示每个原子的震荡值（1&nbsp;</span><span style="font-size:11.0000pt;font-family:'Arial';">≤</span><span style="font-size:11.0000pt;font-family:'微软雅黑';">&nbsp;a</span><span style="font-size:11.0000pt;font-family:'微软雅黑';vertical-align:sub;">n</span><span style="font-size:11.0000pt;font-family:'Arial';">≤</span><span style="font-size:11.0000pt;font-family:'微软雅黑';">&nbsp;1000</span><span style="font-size:11.0000pt;font-family:'微软雅黑';">）</span><span style="font-size:11.0000pt;font-family:'微软雅黑';"></span> </p>

<p class="p0" style="text-indent:21.0000pt;text-align:justify;vertical-align:;"> <span style="font-size:11.0000pt;font-family:'微软雅黑';">如果可以通电输出“YES”，&nbsp;不可以输出“NO”（没有双引号）</span><span style="font-size:11.0000pt;font-family:'微软雅黑';"></span> </p>