PROBLEM LINK:

Practice
Contest

Author:Dmytro Berezin
Tester:Sergey Kulik
Editorialist:Lalit Kundu

DIFFICULTY:

CAKEWALK

PREREQUISITES:

AD-HOC

PROBLEM:

Chef is at x=0.
1-jump: he will move from x -> x + 1
2-jump: he will move from x -> x + 2
3-jump: he will move from x -> x + 3
He will perform a lot of jumps in such a sequence: 1-jump, 2-jump, 3-jump, 1-jump, 2-jump, 3-jump, 1-jump, and so on.
Given an integer 0 ≤ a ≤ 10¹⁸, find will he ever arrive at a.

QUICK EXPLANATION:

In one sequence of 1-jump, 2-jump and 3-jump, he moves from x -> x + 6. So, if intermediate jumps are removed for a minute, x will always be a multiple of 6. Now, if we consider intermediate jumps, we will also consider points of form 6*k - 3, 6*k - 5.

Therefore,

a=input()    
if a%6==0 || a%6==1 || a%6==3:    
     print "yes"    
else:
     print "no"

Complexity: O(1)

AUTHOR'S AND TESTER'S SOLUTIONS:

Author's solution
Setter's solution