3SUM

import sys
from collections import deque

def solve():
    n, x = map(int, input().split())
    array = list(map(int, input().split()))
    array = [(v, i+1) for i, v in enumerate(array)]
    array.sort()
    
    for i in range(len(array)):
        left = 0
        right = len(array) - 1
        sum_value = 0
        
        while left != right:
            sum_value = array[left][0] + array[right][0] + array[i][0]
            
            if sum_value == x: # Value found
                #Check that there is not overlapping
                if left == i:
                    left += 1
                elif right == i:
                    right -= 1
                # Else correct solution
                else: 
                    print(f"{array[left][1]} {array[right][1]} {array[i][1]}")
                    return
                    
            else: 
                
                if sum_value > x:
                    right -= 1
                else:
                    left += 1
                
    print("IMPOSSIBLE")
    
    return
        
                

            
        
        
        
        
        
    
    

    


if __name__ == '__main__':
    solve()

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