Problem:
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The Maximum Number of Customers

$N$ persons visited a restaurant. The restaurant is open from 0 to $T$. The $i$-th person entered the restaurant at $l_i$ and left at $r_i$. Find the maximum number of persons during the business hours.

Constraints

$ 1 \leq N \leq 10^5 $

$ 1 \leq T \leq 10^5 $

$ 0 \leq l_i < r_i \leq T $

Input

The input is given in the following format.

$N$ $T$

$l_1$ $r_1$

$l_2$ $r_2$

:

$l_N$ $r_N$

Output

Print the maximum number of persons in a line.

Sample Input 1

6 10
0 2
1 3
2 6
3 8
4 10
5 10

Sample Output 1

4

Sample Input 2

2 2
0 1
1 2

Sample Output 2

1

Solution in C++ (judge verdict: Accepted)

#include<bits/stdc++.h>
using namespace std;
typedef pair<int,int> P;
int N,T;

vector< P > t;

int main(){
  cin>>N>>T;
  for(int i=0;i<N;i++){
    int l,r;
    cin>>l>>r;
    t.push_back( P(l,1) );
    t.push_back( P(r,-1) );
  }
  sort(t.begin(),t.end());
  int sum=0;
  int ans=0;
  for(int i=0;i<N+N;i++){
    sum+=t[i].second;
    ans=max(ans,sum);
  }
  cout<<ans<<endl;
  return 0;
}