1641.cpp

#include <bits/stdc++.h>
 
#define ll long long
 
using namespace std;
 
int main()
{
    ll n, x;
    cin >> n >> x;
    vector<pair<ll, ll>> arr;    
    int m = 0;
 
    for(ll i = 1; i <= n; i++)
    {
		ll a; 
        cin >> a;
		pair<ll, ll> p; 
        p.first = a; 
        p.second = i;
		arr.push_back(p);
	}
 
    sort(begin(arr), end(arr));
 
    for(ll i = 0; i < n; i++)
    {
		ll l = 0, r = n - 1;
		ll target = x - arr.at(i).first;
 
        while(l != r)
        {			
            if(l != i && r != i && arr.at(l).first + arr.at(r).first == target)
            {    
                m = 1;
				cout << arr.at(i).second << " " << arr.at(l).second << " " << arr.at(r).second << "\n";
                break;
            }
			if(arr.at(l).first + arr.at(r).first < target)
				l++;
			else
				r--;
		}
 
        if(m == 1)
            break;
	}
 
    if(m == 0)
    {
        cout << "IMPOSSIBLE" << "\n";
    }
    
    return 0;
}