Problem:
Score : 400 points

Problem Statement

Joisino is planning to record N TV programs with recorders.

The TV can receive C channels numbered 1 through C.

The i-th program that she wants to record will be broadcast from time s_i to time t_i (including time s_i but not t_i) on Channel c_i.

Here, there will never be more than one program that are broadcast on the same channel at the same time.

When the recorder is recording a channel from time S to time T (including time S but not T), it cannot record other channels from time S-0.5 to time T (including time S-0.5 but not T).

Find the minimum number of recorders required to record the channels so that all the N programs are completely recorded.

Constraints

1≤N≤10^5

1≤C≤30

1≤s_i<t_i≤10^5

1≤c_i≤C

If c_i=c_j and i≠j, either t_i≤s_j or s_i≥t_j.

All input values are integers.

Input

Input is given from Standard Input in the following format:

N C
s_1 t_1 c_1
:
s_N t_N c_N

Output

When the minimum required number of recorders is x, print the value of x.

Sample Input 1

3 2
1 7 2
7 8 1
8 12 1

Sample Output 1

2

Two recorders can record all the programs, for example, as follows:

With the first recorder, record Channel 2 from time 1 to time 7. The first program will be recorded. Note that this recorder will be unable to record other channels from time 0.5 to time 7.

With the second recorder, record Channel 1 from time 7 to time 12. The second and third programs will be recorded. Note that this recorder will be unable to record other channels from time 6.5 to time 12.

Sample Input 2

3 4
1 3 2
3 4 4
1 4 3

Sample Output 2

3

There may be a channel where there is no program to record.

Sample Input 3

9 4
56 60 4
33 37 2
89 90 3
32 43 1
67 68 3
49 51 3
31 32 3
70 71 1
11 12 3

Sample Output 3

2

Solution in C++14 (GCC 5.4.1) (judge verdict: Accepted)

#include <bits/stdc++.h>
#include <math.h>
#define _GLIBCXX_DEBUG
#define _LIBCPP_DEBUG 0

using namespace std;
#define ll long long
#define rep(i,n) for (int i = 0; i < n; i++)
#define rrep(i,n) for (int i = n-1; i >= 0; i--)
#define MOD (1000000007)
#define vi vector<int>
#define vl vector<ll>
#define vb vector<bool>
#define vvi vector<vi>
#define vvl vector<vl>
#define vvb vector<vb>
#define pii pair<int, int>
#define pli pair<ll, int>
#define pll pair<ll, ll>
#define pb push_back

#define mp make_pair
#define all(a) (a).begin(),(a).end()

template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return true; } return false; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return true; } return false; }

ll gcd(ll a, ll b) {
    if (b == 0) return a;
    else return gcd(b, a % b);
}

ll keta(ll n){
  string s = to_string(n);
  ll num = s.size();
  return num;
}

const ll INF = 1LL << 60;

const int dh[4] = {1,0,-1,0};
const int dw[4] = {0,1,0,-1};

struct Edge{
  int to;
  int weight;
  Edge(int t, int w) : to(t), weight(w){}
};
using Graph = vector<vector<Edge>>;
using P = pair<ll, int>;

class UnionFind{
public:
  vi Parent, diff_weight;
  UnionFind(int n){
    Parent = vi(n,-1);
    diff_weight = vi(n,0);
  }

  int root(int a){
    if(Parent[a] < 0) return a;
    int r = root(Parent[a]);
    diff_weight[a] += diff_weight[Parent[a]];
    return Parent[a] = r;
  }

  int weight(int a){
    root(a);
    return diff_weight[a];
  }

  bool issame(int a, int b){
    return root(a) == root(b);
  }

  int size(int a){
    return -Parent[root(a)];
  }

  bool merge(int a, int b, int w = 0){
    w += weight(a); w -= weight(b);

    a = root(a);
    b = root(b);

    if(a == b) return false;

    if(size(a) < size(b)) swap(a,b), w = -w;
    Parent[a] += Parent[b];
    Parent[b] = a;
    diff_weight[b] = w;
    return true;
  }

  int diff(int a, int b){
    return weight(b) - weight(a);
  }
};

vi MP(string s){
  vi A(s.size()+1);
  A[0] = -1;
  int j = -1;
  rep(i,s.size()) {
    while(j >= 0 && s[i] != s[j]) j = A[j];
    j++;
    A[i+1] = j;
  }
  return A;
}

vi Manacher(string s){
  vi R(s.size());
  int i = 0, j = 0;
  while(i < s.size()){
    while(i-j >= 0 && i+j < s.size() && s[i-j] == s[i+j]) ++j;
    R[i] = j;
    int k = 1;
    while(i-k >= 0 && i+k < s.size() && k+R[i-k] < j) R[i+k] = R[i-k], k++;
    i += k; j -= k;
  }
  return R;
}

vi Z_algorithm(string &s){
  vi Z(s.size());
  Z[0] = s.size();
  int i = 1, j = 0;
  while(i < s.size()){
    while(i+j < s.size() && s[j] == s[i+j]) j++;
    Z[i] = j;
    if(j == 0){++i; continue;}
    int k = 1;
    while(i+k < s.size() && k+Z[k] < j) Z[i+k] = Z[k], ++k;
    i += k; j -= k;
  }
  return Z;
}

const int MAX = 1e6+1;

long long fac[MAX], finv[MAX], inv[MAX];

// テーブルを作る前処理
void COMinit() {
    fac[0] = fac[1] = 1;
    finv[0] = finv[1] = 1;
    inv[1] = 1;
    for (int i = 2; i < MAX; i++){
        fac[i] = fac[i - 1] * i % MOD;
        inv[i] = MOD - inv[MOD%i] * (MOD / i) % MOD;
        finv[i] = finv[i - 1] * inv[i] % MOD;
    }
}

// 二項係数計算
long long COM(ll n, ll k){
  if(n >= MAX){
    ll tmp = 1;
    rep(i,k){
      tmp *= (n-i);
      tmp %= MOD;
    }
    return tmp*finv[k]%MOD;
  }

  if (n < k) return 0;
  if (n < 0 || k < 0) return 0;
  return fac[n] * (finv[k] * finv[n - k] % MOD) % MOD;
}

ll POW(ll x, ll n){
  ll ret = 1;
  if(n < 0){// n < 0 にも対応
    n *= -1;
    x = inv[x];
  }
  while(0 < n){
    if(n%2 == 0){
      x = x*x%MOD;
      n /= 2;
    }
    else{
      ret = ret*x%MOD;
      n--;
    }
  }
  return ret;
}

const int m = 100000+5;

int imos[30][m];
int sum[m];

int main(){
  int n, C; cin >> n >> C;
  rep(i,n) {
    int s, t, c; cin >> s >> t >> c;
    c--;
    for(int i = s; i < t+1; i++) {
      imos[c][i] = 1;
    }
  }
  rep(c,C) {
    rep(i,m) sum[i] += imos[c][i];
  }
  int ans = 0;
  rep(i,m) chmax(ans, sum[i]);
  cout << ans << endl;
}