//  Sum of Two Values

#include<bits/stdc++.h>

using namespace std;
using ll = long long;

int main() {
    map<ll, vector<int>> input;
    int n; cin >> n;
    ll x; cin >> x;
    vector<ll> in;
    for (int i{}; i < n; i++) {
        ll a; cin >> a;
        input[a].push_back(i);
        in.push_back(a);
    }
    for (int i{}; i < n; i++) {
        ll target = x - in[i];
        bool flag = target == in[i];
        if (input[target].empty() || (input[target].size() == 1 && flag)) continue;
        else {
            if (flag) {
                cout << i + 1 << " " << input[target][1] + 1<< endl;
            } else {
                cout << i + 1 <<  " " << input[target][0] + 1<< endl;
            }
            return 0;
        }
    }
    cout << "IMPOSSIBLE" << endl;
    return 0;
}