A large triangle is divided evenly into exactly eight rows of smaller unit triangles, like so:
^
/0\ <-- Row 1
/___\
/1\2/3\ <-- Row 2
/___V___\
/4\5/6\7/8\ <-- Row 3
/___V___V___\ .
/ . . . \ . ___
/ . . . \ . ('v') (\_/)
/ . . . \ <-- Row 8 ((___)) (^x^)
/___________________\ ^ ^ c(_)o
The unit triangles are position-numbered (in reading order) starting from zero.
You can flip any set of unit triangles that make up (in shape, not necessarily in shade) one larger, upright, and three-row-high triangle.
Flipping reverses the shade of each of its nine unit triangles individually (shaded triangles become unshaded, vice versa).
Given an unlimited number of flips, is it possible to unify (in shade) the entire triangle?
Input Specification
The first line of input contains integer
The next line contains
Output Specification
Output YES
or NO
, whether or not it is possible to make the entire triangle the same shade (i.e. all shaded or all unshaded).
Sample Input 1
16
29 44 32 11 28 45 30 33 19 42 22 46 20 18 27 43
Sample Output 1
YES
Sample Input 2
1
2
Sample Output 2
NO
Comments