3SUM

import sys

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

if len(array) < 3:
    print("IMPOSSIBLE")
    sys.exit()

array2 = array.copy()
array2.sort()

for i in range(0,n-2):
    a = array2[i]
    start = i+1
    end = n-1
    while start < end:
        b = array2[start]
        c = array2[end]
        if (a + b + c) == x:
            print(array.index(a)+1, end=' ')
            print(array.index(b)+1, end=' ')
            print(array.index(c)+1)
            sys.exit()
        elif (a + b + c) > x:
            end = end - 1
        else:
            start = start + 1

print("IMPOSSIBLE")

Test 1

Verdict: ACCEPTED

Test 2

Verdict: ACCEPTED

Test 3

Verdict: ACCEPTED

Test 4

Verdict: ACCEPTED

Test 5

Verdict: WRONG ANSWER

Test 6

Verdict: WRONG ANSWER

Test 7

Verdict: WRONG ANSWER

Test 8

Verdict: WRONG ANSWER

Test 9

Verdict: WRONG ANSWER

Test 10

Verdict: ACCEPTED

Test 11

Verdict: WRONG ANSWER

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