Happy Number

Difficulty: 1200 2000 ms 128 MB

math implementation

Repeatedly replace N by the sum of the squares of its digits. If the process reaches 1, N is happy; if it enters a cycle, it is not. Decide for N.

Input: one integer N.

Output: YES if N is happy, else NO.

Constraints:

• 1 ≤ N ≤ 10¹⁸

Sample Tests

19

YES

4

NO

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