const int N = 400005;
const int LG = 21;
const int MOD = 1e9 + 7;
const int INF = 1e9;

#include <iostream>
#include <vector>
#include <string>
#include <map>
#include <set>
#include <algorithm>
#include <cmath>
#include <time.h>
#include <unordered_set>
#include <bitset>
#include <deque>

using namespace std;

typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef vector<ll> vi;

#define forn(i, n) for (int (i) = 0; (i) != (n); (i)++)
#define all(v) (v).begin(), (v).end()
#define rall(v) (v).rbegin(), (v).rend()
#define popcount(x) __builtin_popcount(x)
#define popcountll(x) __builtin_popcountll(x)
#define fi first
#define se second
#define re return

#ifdef LOCAL
#define dbg(x) cerr << __LINE__ << " " << #x << " " << x << endl
#define ln cerr << __LINE__ << endl
#else
#define dbg(x) void(0)
#define ln void(0)
#endif // LOCAL

ll inq(ll x, ll y)
{
    if (!y) re 1 % MOD;
    ll l = inq(x, y / 2);
    if (y % 2) re l * l % MOD * x % MOD;
    re l * l % MOD;
}

ll rev(ll x)
{
    return inq(x, MOD - 2);
}

bool __precomputed_combinatorics = 0;
vector<ll> __fact, __ufact, __rev;

void __precompute_combinatorics()
{
    __precomputed_combinatorics = 1;
    __fact.resize(N);
    __ufact.resize(N);
    __rev.resize(N);
    __rev[1] = 1;
    for (int i = 2; i < N; i++) __rev[i] = MOD - __rev[MOD % i] * (MOD / i) % MOD;
    __fact[0] = 1, __ufact[0] = 1;
    for (int i = 1; i < N; i++) __fact[i] = __fact[i - 1] * i % MOD, __ufact[i] = __ufact[i - 1] * __rev[i] % MOD;
}

ll fact(int x)
{
    if (!__precomputed_combinatorics) __precompute_combinatorics();
    return __fact[x];
}

ll cnk(int n, int k)
{
    if (!__precomputed_combinatorics) __precompute_combinatorics();
    return __fact[n] * __ufact[n - k] % MOD * __ufact[k] % MOD;
}

int ans = 0;
int n, m;
int L[N], R[N];
pair<int, int> p[N];

int Tree[4 * N];
int Push[4 * N];

void push(int L, int M, int R, int V)
{
    Tree[2 * V + 1] += Push[V];
    Push[2 * V + 1] += Push[V];
    Tree[2 * V + 2] += Push[V];
    Push[2 * V + 2] += Push[V];
    Push[V] = 0;
}

void Add(int l, int r, int val, int L = 0, int R = N, int V = 0)
{
    if (r <= L || R <= l) return;
    if (l <= L && R <= r)
    {
        Tree[V] += val;
        Push[V] += val;
        return;
    }
    int M = (L + R) / 2;
    push(L, M, R, V);
    Add(l, r, val, L, M, 2 * V + 1);
    Add(l, r, val, M, R, 2 * V + 2);
    Tree[V] = max(Tree[2 * V + 1], Tree[2 * V + 2]);
}

int Get(int l, int r, int L = 0, int R = N, int V = 0)
{
    if (r <= L || R <= l) return -INF;
    if (l <= L && R <= r)
    {
        return Tree[V];
    }
    int M = (L + R) / 2;
    push(L, M, R, V);
    return max(Get(l, r, L, M, 2 * V + 1), Get(l, r, M, R, 2 * V + 2));
}

signed main()
{
    srand(time(NULL));
    #ifdef ONLINE_JUDGE
        ios_base::sync_with_stdio(false);
        cin.tie(0);
        cout.tie(0);
    #endif // ONLINE_JUDGE
    cin >> n >> m;
    for (int i = 0; i < n; i++)
    {
        cin >> L[i] >> R[i];
    }
    ans = max(ans, n - m);
    for (int i = 0; i < n; i++) p[i] = {L[i], R[i]};
    sort(p, p + n);
    for (int t = m; t >= 1; t--)
    {
        Add(0, t + 1, -1);
    }
    for (int i = 0; i < n; i++)
    {
        //cout << p[i].fi << " " << p[i].se << "\n";
        Add(0, p[i].se + 1, 1);
        //cout << Get(p[i].fi, N) - p[i].fi << "\n";
        ans = max(ans, Get(p[i].fi + 1, N) - p[i].fi);
    }
    cout << ans;
}

/* Note:
Check constants at the beginning of the code.
N is set to 4e5 but be careful in problems with large constant factor.
Check corner cases.
No def int long long for now.
*/


Measured memory_bytes: 13568