c.cpp

#include <bits/stdc++.h>

using namespace std;

struct Segment {
    int left, right, id;
};

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(0); cout.tie(0);

    int n; cin >> n;

    if (n == 1) {
        cout << "-1 -1" << endl;
        return 0;
    }

    vector<Segment> segs;
    for (int i = 1; i <= n; ++i) {
        int l, r;
        cin >> l >> r;
        segs.push_back(Segment{l, r, i});
    }

    sort(segs.begin(), segs.end(), [](const Segment& a, const Segment& b) {
        return a.left < b.left || (a.left == b.left && (a.right < b.right || (a.right == b.right && a.id < b.id)));
    });

    int prev = 0;
    for (int curr = 1; curr < n; ++curr) {
        assert(segs[prev].left <= segs[curr].left);
        if (segs[curr].right > segs[prev].right) {
            prev = curr;
        } else {
            assert(prev != curr);
            assert(segs[prev].left <= segs[curr].left && segs[curr].right <= segs[prev].right);
            cout << segs[curr].id << " " << segs[prev].id << endl;
            return 0;
        }
    }
    cout << "-1 -1" << endl;
    return 0;
}