#include <bits/stdc++.h>
using namespace std;

using ll = long long;
#define rep(i, n) for(ll i = 0; i < (n); ++i)
#define rep2(i, l, r) for(ll i = (l); i < (r); ++i)

using vi = vector<int>;
using vvi = vector<vi>;
using vll = vector<ll>;

#define all(A) A.begin(), A.end()
#define elif else if
using pii = pair<ll, ll>;

bool chmin(auto &a, auto b) {return a > b ? a = b, 1 : 0;}
bool chmax(auto &a, auto b) {return a < b ? a = b, 1 : 0;}

struct IOS {
  IOS() {
    cin.tie(0);
    ios::sync_with_stdio(0);
  }
} iosetup;


template<class T>
void print(vector<T> a) {
  for(auto x : a) cout << x << ' ';
  cout << endl;
}

void print(auto x) {
  cout << x << endl;
}

template<class Head, class... Tail>
void print(Head &&head, Tail &&...tail) {
  cout << head << ' ';
  print(forward<Tail>(tail)...);
}

struct edge {
  ll to, cost;
  edge() = default;
  edge(ll t, ll c) : to(t), cost(c) { }
};

void solve() {
  ll N, F; cin >> N >> F;
  vector<array<ll, 2>> LR(N);
  rep(i, N) {
    ll a, b; cin >> a >> b;
    LR[i] = {a, b};
  }

  set<ll> zat;
  for(auto [a, b] : LR) {
    zat.insert(a);
    zat.insert(b);
  }
  zat.insert(F);

  vector<ll> h;
  map<ll, ll> mp;
  ll siz = 0;
  for(auto x : zat) {
    h.emplace_back(x);
    mp[x] = siz++;
  }
  assert((ll)h.size() == siz);

  vector graph(N, vector<edge>());
  rep(i, siz-1) {
    graph[i].push_back(edge(i+1, h[i+1] - h[i]));
    graph[i+1].push_back(edge(i, 0));
  }
  for(auto [l, r] : LR) {
    ll u = mp[l], v = mp[r];
    graph[u].push_back(edge(v, 0));
  }

  const ll INF = 1e15;
  vector<ll> dist(siz, INF);
  {
    priority_queue< array<ll, 2>, vector<array<ll, 2>>, greater<array<ll, 2>> > pq;
    ll r = mp[F];
    dist[r] = 0;
    pq.emplace(dist[r], r);
    while(pq.size()) {
      auto [d, v] = pq.top();
      pq.pop();
      if(dist[v] < d) continue;
      for(auto e : graph[v]) {
        if(chmin(dist[e.to], dist[v] + e.cost)) {
          pq.emplace(dist[e.to], e.to);
        }
      }
    }
  }

  ll mx = 0, base = 0;
  for(auto [l, r] : LR) {
    chmax(mx, r);
    base += (r - l);
  }
  ll diff = dist[mp[mx]];
  ll res = base + diff;
  cout << res << '\n';

  return;
}

int main() {
hoge
  ll T; cin >> T;
  while(T--) {
    solve();
  }

  return 0;
}

answer.code: In function ‘int main()’:
answer.code:115:1: error: ‘hoge’ was not declared in this scope
  115 | hoge
      | ^~~~
answer.code:116:16: error: ‘T’ was not declared in this scope
  116 |   ll T; cin >> T;
      |                ^
In file included from /usr/include/c++/14/ext/alloc_traits.h:34,
                 from /usr/include/c++/14/bits/basic_string.h:39,
                 from /usr/include/c++/14/string:54,
                 from /usr/include/c++/14/bitset:52,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:52,
                 from answer.code:1:
/usr/include/c++/14/bits/alloc_traits.h: In instantiation of ‘static constexpr void std::allocator_traits<std::allocator<_CharT> >::construct(allocator_type&, _Up*, _Args&& ...) [with _Up = std::array<long long int, 2>; _Args = {long long int&, long long int&}; _Tp = std::array<long long int, 2>; allocator_type = std::allocator<std::array<long long int, 2> >]’:
/usr/include/c++/14/bits/vector.tcc:117:30:   required from ‘constexpr std::vector<_Tp, _Alloc>::reference std::vector<_Tp, _Alloc>::emplace_back(_Args&& ...) [with _Args = {long long int&, long long int&}; _Tp = std::array<long long int, 2>; _Alloc = std::allocator<std::array<long long int, 2> >; reference = std::array<long long int, 2>&]’
  117 |             _Alloc_traits::construct(this->_M_impl, this->_M_impl._M_finish,
      |             ~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  118 |                                      std::forward<_Args>(__args)...);
      |                                      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/bits/stl_queue.h:754:18:   required from ‘void std::priority_queue<_Tp, _Sequence, _Compare>::emplace(_Args&& ...) [with _Args = {long long int&, long long int&}; _Tp = std::array<long long int, 2>; _Sequence = std::vector<std::array<long long int, 2> >; _Compare = std::greater<std::array<long long int, 2> >]’
  754 |           c.emplace_back(std::forward<_Args>(__args)...);
      |           ~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
answer.code:89:15:   required from here
   89 |     pq.emplace(dist[r], r);
      |     ~~~~~~~~~~^~~~~~~~~~~~
/usr/include/c++/14/bits/alloc_traits.h:536:28: error: no matching function for call to ‘construct_at(std::array<long long int, 2>*&, long long int&, long long int&)’
  536 |           std::construct_at(__p, std::forward<_Args>(__args)...);
      |           ~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In file included from /usr/include/c++/14/bits/stl_iterator.h:78,
                 from /usr/include/c++/14/bits/stl_algobase.h:67,
                 from /usr/include/c++/14/algorithm:60,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:51:
/usr/include/c++/14/bits/stl_construct.h:94:5: note: candidate: ‘template<class _Tp, class ... _Args> constexpr decltype (::new(void*(0)) _Tp) std::construct_at(_Tp*, _Args&& ...)’
   94 |     construct_at(_Tp* __location, _Args&&... __args)
      |     ^~~~~~~~~~~~
/usr/include/c++/14/bits/stl_construct.h:94:5: note:   template argument deduction/substitution failed:
/usr/include/c++/14/bits/stl_construct.h: In substitution of ‘template<class _Tp, class ... _Args> constexpr decltype (::new(void*(0)) _Tp) std::construct_at(_Tp*, _Args&& ...) [with _Tp = std::array<long long int, 2>; _Args = {long long int&, long long int&}]’:
/usr/include/c++/14/bits/alloc_traits.h:536:21:   required from ‘static constexpr void std::allocator_traits<std::allocator<_CharT> >::construct(allocator_type&, _Up*, _Args&& ...) [with _Up = std::array<long long int, 2>; _Args = {long long int&, long long int&}; _Tp = std::array<long long int, 2>; allocator_type = std::allocator<std::array<long long int, 2> >]’
  536 |           std::construct_at(__p, std::forward<_Args>(__args)...);
      |           ~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/bits/vector.tcc:117:30:   required from ‘constexpr std::vector<_Tp, _Alloc>::reference std::vector<_Tp, _Alloc>::emplace_back(_Args&& ...) [with _Args = {long long int&, long long int&}; _Tp = std::array<long long int, 2>; _Alloc = std::allocator<std::array<long long int, 2> >; reference = std::array<long long int, 2>&]’
  117 |             _Alloc_traits::construct(this->_M_impl, this->_M_impl._M_finish,
      |             ~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  118 |                                      std::forward<_Args>(__args)...);
      |                                      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/bits/stl_queue.h:754:18:   required from ‘void std::priority_queue<_Tp, _Sequence, _Compare>::emplace(_Args&& ...) [with _Args = {long long int&, long long int&}; _Tp = std::array<long long int, 2>; _Sequence = std::vector<std::array<long long int, 2> >; _Compare = std::greater<std::array<long long int, 2> >]’
  754 |           c.emplace_back(std::forward<_Args>(__args)...);
      |  ...