3SUM

input/code.cpp: In function 'int main()':
input/code.cpp:20:10: error: 'sort' is not a member of 'std'; did you mean 'qsort'?
   20 |     std::sort(arr.begin(), arr.end());
      |          ^~~~
      |          qsort

#include <iostream>
#include <vector>

using namespace std;
typedef long long ll;

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    ll n, x;
    cin >> n >> x;
    vector<pair<ll, int>> arr(n);
    for (int i = 0; i < n; i++) {
        ll val;
        cin >> val;
        arr[i] = {val, i};
    }

    std::sort(arr.begin(), arr.end());

    for (int i = 0; i < n; i++) {
        for (int j = i + 1; j < n; j++) {
            for (int k = j + 1; k < n; k++) {

                ll sum = arr[i].first + arr[j].first + arr[k].first;

                if (sum > x) {
                    cout << "IMPOSSIBLE\n";
                    return 0;
                }

                if (sum == x) {
                    cout << arr[i].second + 1 << " " << arr[j].second + 1 << " "
                         << arr[k].second + 1 << "\n";
                    return 0;
                }
            }
        }
    }

    cout << "IMPOSSIBLE\n";
    return 0;
}