3SUM

n, x = [int(x) for x in input().split()]
array = [(int(x),i) for i, x in enumerate(input().split())]
array.sort()

def triplet(array, x):
    for i in range(n-2):
        left = i+1
        right = len(array)-1
        sum = x - array[i][0]
        while left < right:
            if array[left][0]+array[right][0] == sum:
                return [array[i][1], array[left][1], array[right][1]]
            if array[left][0] + array[right][0] < sum:
                left += 1
            else:
                right -=1
    return []

res = triplet(array, x)
if len(res) > 0:
    for nbr in res:
        print(nbr+1, end=' ')
else:
    print('IMPOSSIBLE')

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

Test 23

Verdict: ACCEPTED