52pts求调

#include<bits/stdc++.h>
using namespace std;
long long m,d,n,a[500010],flg,ans;
bool cmp(int x,int y)
{
	return x>y;
}
int main()
{
	cin>>m>>d>>n;
	for(int i=1;i<=n;i++) cin>>a[i];
	sort(a+1,a+1+n,cmp);
	int l=1,r=n;
	while(l<r)
	{
		int mid=(l+r+1)>>1;
		if(a[mid]>=m-d) l=mid;
		else if(a[mid]<m-d) r=mid-1;
	}
	if(a[1]<d||a[l]<m-d) 
	{
		cout<<0;
		return 0;
	}
	for(int i=1;i<=n;i++)
	{
		if(i==l) continue;
		if(a[i]-(d-flg)>0) 
		{
			flg+=a[i]-(d-flg);
			ans++;
		}
		else 
		{
			cout<<0;
			return 0;
		}
		if(flg>d) break;
	}
	cout<<ans+1;
	return 0;
}