#include <bits/stdc++.h>
using namespace std;
pair<pair<long long, long long>, long long> merge_p(
    pair<long long, long long> a, pair<long long, long long> b) {
  if (a.first > b.first) swap(a, b);
  if (b.first <= a.second) {
    if (b.second <= a.second)
      return make_pair(b, 0);
    else
      return make_pair(make_pair(b.first, a.second), 0);
  } else {
    return make_pair(make_pair(a.second, b.first), b.first - a.second);
  }
}
void solve() {
  int n, x;
  cin >> n >> x;
  pair<long long, long long> opt = make_pair(x, x);
  long long ans = 0;
  pair<long long, long long> tmp;
  for (int i = 0; i < n; ++i) {
    cin >> tmp.first >> tmp.second;
    pair<pair<long long, long long>, long long> f = merge_p(opt, tmp);
    opt = f.first;
    ans += f.second;
  }
  cout << ans << endl;
}
int main() {
  time_t t1 = clock();
  solve();
  time_t t2 = clock();
}
