#include <bits/stdc++.h>
using namespace std;
const long long md = 1e9 + 7;
const long long MX = 2e5 + 5;
const long long INF = 1e18;
const long double PI = 4 * atan((long double)1);
long long power_md(long long a, long long n) {
  long long res = 1;
  while (n) {
    if (n % 2) res = (res % md * a % md) % md;
    a = (a % md * a % md) % md;
    n /= 2;
  }
  res %= md;
  return res;
}
long long power(long long a, long long n) {
  long long res = 1;
  while (n) {
    if (n % 2) res *= a;
    a = a * a;
    n /= 2;
  }
  return res;
}
long long abst(long long a) { return ((a < 0) ? (-1 * a) : (a)); }
class cmp_set {
 public:
  bool operator()(long long a, long long b) { return a > b; }
};
vector<string> vec_splitter(string s) {
  s += ',';
  vector<string> res;
  while (!s.empty()) {
    res.push_back(s.substr(0, s.find(',')));
    s = s.substr(s.find(',') + 1);
  }
  return res;
}
void debug_out(vector<string> __attribute__((unused)) args,
               __attribute__((unused)) long long idx,
               __attribute__((unused)) long long LINE_NUM) {
  cerr << endl;
}
template <typename Head, typename... Tail>
void debug_out(vector<string> args, long long idx, long long LINE_NUM, Head H,
               Tail... T) {
  if (idx > 0)
    cerr << ", ";
  else
    cerr << "Line(" << LINE_NUM << ") ";
  stringstream ss;
  ss << H;
  cerr << args[idx] << " = " << ss.str();
  debug_out(args, idx + 1, LINE_NUM, T...);
}
long long n, s;
vector<pair<long long, long long> > v;
long long fun(long long x) {
  long long req = 0;
  long long cnt = 0;
  for (long long i = v.size() - 1; i >= 0; i--) {
    if (cnt == ((n / 2) + 1)) break;
    if (v[i].second < x)
      continue;
    else {
      cnt++;
      req += max((long long)0, x - v[i].first);
    }
  }
  if (cnt < ((n / 2) + 1)) return 0;
  if (req > s) return 0;
  return 1;
}
int32_t main() {
  ios_base::sync_with_stdio(false), cin.tie(NULL);
  long long t;
  cin >> t;
  while (t--) {
    v.clear();
    cin >> n >> s;
    long long sum = 0;
    for (long long i = 0; i < n; i++) {
      long long l, r;
      cin >> l >> r;
      v.push_back({l, r});
      sum += l;
    }
    sort(v.begin(), v.end());
    s -= sum;
    long long lo = v[n / 2].first, hi = 1e9, mid;
    while (lo < hi) {
      mid = lo + (hi - lo + 1) / 2;
      if (fun(mid))
        lo = mid;
      else
        hi = mid - 1;
    }
    cout << lo << "\n";
  }
  return 0;
}
