t.cpp

#include <iostream>
#include <vector>
#include <algorithm>
#include <math.h>
using namespace std;

int main()
{
	// input
	int n,w,tmp,res=0,flag;
	cin >> n;
	cin >> w;
	vector<int> weight(n,0);
	flag = n;
	// vector<bool> flag(n,0);
	for(int i = 0; i < n ; i++){
		cin >> tmp;
		weight[i] = tmp;
	}
	// sort
	sort(weight.begin(), weight.end());

	// combine
	// 排序后，首尾指针往中间逼近
	int l=0,r=weight.size()-1;
	while(l<r){
		if(weight[l]+weight[r] <= w){
			l++;
		}else{
			res+=2;
			flag-=2;
			l++;
			r--;
		}
	}
	res += (int) ceil(flag/2.0);
	cout <<res <<endl;
}