考试时的40分代码：

#include<bits/stdc++.h>
using namespace std;
const int mm=100005;
int ne[mm],wa[mm],lq[mm];
int n,my1,my2,ans;
struct node{
	int s=0;
	int e=0;
}m1[mm],m2[mm];
bool cmp(node x,node y)
{
	return x.s<y.s;
}
inline int read()
{
	int x=0,f=1;char ch=getchar();
	while(ch<'0'||ch>'9') {if(ch=='-') f=-1; ch=getchar();}
	while(ch>='0'&&ch<='9') {x=(x<<3)+(x<<1)+(ch-'0'); ch=getchar();}
	return x*f;
}

int main()
{
	n=read();my1=read();my2=read();
	for(int i=1;i<=my1;i++)
	{
		m1[i].s=read();
		m1[i].e=read();
	}
	sort(m1+1,m1+my1+1,cmp);
	for(int i=1;i<=my1;i++)
	{
		for(int j=1;j<=n;j++)
		{
			if(lq[j]<=m1[i].s)
			{
				lq[j]=m1[i].e;
				ne[j]++;
				break;
			}
		}
	}
	memset(lq,0,sizeof(lq));
	for(int i=1;i<=my2;i++)
	{
		m2[i].s=read();
		m2[i].e=read();
	}
	sort(m2+1,m2+my2+1,cmp);
	for(int i=1;i<=my2;i++)
	{
		for(int j=1;j<=n;j++)
		{
			if(lq[j]<=m2[i].s)
			{
				lq[j]=m2[i].e;
				wa[j]++;
				break;
			}
		}
	}
	for(int i=n;i>=1;i--)
	{
		int xx=0;
		for(int j=0;j<=i;j++) xx+=ne[j];
		for(int j=0;j<=n-i;j++) xx+=wa[j];
		ans=max(ans,xx);
	}
	cout<<ans;
	return 0;
	return 0;
}

估计神犇们都笑抽筋了吧
脑子清醒后优化的100分代码：

#include<bits/stdc++.h>
using namespace std;
const int mm=100005;
int ne[mm],wa[mm],lq[mm];
int n,my1,my2,ans;
struct node{
	int s=0;
	int e=0;
}m1[mm],m2[mm];
bool cmp(node x,node y)
{
	return x.s<y.s;
}
inline int read()
{
	int x=0;char ch=getchar();
	while(ch<'0'||ch>'9') {ch=getchar();}
	while(ch>='0'&&ch<='9') {x=(x<<3)+(x<<1)+(ch-'0'),ch=getchar();}
	return x;
}
int main()
{
	n=read(),my1=read(),my2=read();
	for(register int i(1);i<=my1;i++)
	{
		m1[i].s=read(),m1[i].e=read();
	}
	sort(m1+1,m1+my1+1,cmp);
	for(register int i(1);i<=my1;i++)
	{
		for(register int j(1);j<=n;j++)
		{
			if(lq[j]<=m1[i].s)
			{
				lq[j]=m1[i].e;
				ne[j]++;
				break;
			}
		}
	}
	memset(lq,0,sizeof(lq));
	for(register int i=1;i<=my2;i++)
	{
		m2[i].s=read(),m2[i].e=read();
	}
	sort(m2+1,m2+my2+1,cmp);
	for(register int i=1;i<=my2;i++)
	{
		for(register int j=1;j<=n;j++)
		{
			if(lq[j]<=m2[i].s)
			{
				lq[j]=m2[i].e;
				wa[j]++;
				break;
			}
		}
	}
    int xx=0;
    for(register int i=1;i<=n;++i) xx+=ne[i];
    ans=xx;
    for(register int i=n;i>=1;i--)
    {
        xx-=ne[i];
        xx+=wa[n-i+1];
        ans=max(ans,xx);
    }
	cout<<ans;
	return 0;
}