Alien Invasion

#include <bits/stdc++.h>

#define ll long long
#define lll __int128
#define pii pair<int, int>
#define M 1000000007

using namespace std;

int main () {
	ll nn;
	cin>>nn;
	lll n = nn;
	lll ans = 0;
	for (lll x = n; x >= 1; x /= 2) {
		while ((ans + x) * (ans + x) <= n) ans += x;
	}
	if (ans * ans == n) {
		cout<<"odd"<<endl;
	} else {
		cout<<"even"<<endl;
	}
}

Test 1

Verdict: ACCEPTED

Test 2

Verdict: ACCEPTED

Test 3

Verdict: ACCEPTED

Test 4

Verdict: ACCEPTED

Test 5

Verdict: ACCEPTED

Test 6

Verdict: ACCEPTED

Test 7

Verdict: ACCEPTED

Test 8

Verdict: ACCEPTED

Test 9

Verdict: ACCEPTED

Test 10

Verdict: ACCEPTED

Test 11

Verdict: ACCEPTED

Test 12

Verdict: ACCEPTED

Test 13

Verdict: ACCEPTED

Test 14

Verdict: ACCEPTED

Test 15

Verdict: ACCEPTED

Test 16

Verdict: ACCEPTED

Test 17

Verdict: ACCEPTED

Test 18

Verdict: ACCEPTED

Test 19

Verdict: ACCEPTED

Test 20

Verdict: ACCEPTED

Test 21

Verdict: ACCEPTED

Test 22

Verdict: ACCEPTED