public static void main(String[] args) {

System.out.println(isPairedN(new int[] {1, 4, 1, 4, 5, 6}, 5));

System.out.println(isPairedN(new int[] {1, 4, 1, 4, 5, 6}, 6));

System.out.println(isPairedN(new int[] {0, 1, 2, 3, 4, 5, 6, 7, 8}, 6));

System.out.println(isPairedN(new int[] {1, 4, 1}, 5));

System.out.println(isPairedN(new int[] {8, 8, 8, 8, 7, 7, 7}, 15));

System.out.println(isPairedN(new int[] {8, -8, 8, 8, 7, 7, -7}, -15));

System.out.println(isPairedN(new int[] {3}, 3));

System.out.println(isPairedN(new int[] {}, 0));

}

static int isPairedN(int[] a, int n) {

if (a.length <= 1 || n <= 0 || n >= (a.length - 1) * 2)

return 0;

for (int i = 0; i < a.length; i++) {

for (int j = i + 1; j < a.length; j++) {

if (a[i] + a[j] == n && i + j == n) {

return 1;

}

}

}

return 0;

}