Sum Of Two Values

#include <iostream>
#include <unordered_map>
using namespace std;

int main() {
    int n;
    long long x;
    cin >> n >> x;

    unordered_map<long long, int> seen;
    for (int i = 1; i <= n; ++i) {
        long long num;
        cin >> num;
        long long complement = x - num;

        if (seen.count(complement)) {
            // Found the pair
            cout << seen[complement] << " " << i << endl;
            return 0;
        }

        seen[num] = i;
    }

    cout << "IMPOSSIBLE" << endl;
    return 0;
}