#include <bits/stdc++.h>
using namespace std;
const int maxn = 1e6 + 42;
void solve() {
int N;
cin >> N;
int l, r;
map<int, int> open, close;
set<int> ends;
int L = 1, R = 1e9;
for(int i = 0; i < N; i++) {
cin >> l >> r;
ends.insert(l);
ends.insert(r);
L = max(L, l);
R = min(R, r);
open[l]++;
close[r]++;
}
int ans = N;
int balance = 0;
for(auto it = begin(ends); it != prev(end(ends)); ++it) {
balance += open[*it] - close[*it];
if(*it >= R && L >= *next(it)) {
ans = min(ans, balance);
}
}
cout << (ans == N ? -1 : ans) << "\n";
}
signed main() {
//freopen("input.txt", "r", stdin);
int t;
cin >> t;
while(t--) {
solve();
}
}
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