代码（20分的）：

# include <iostream>
# include <iomanip>
# include <cstdio>
# include <cmath>
# include <cstring>
# include <algorithm>
# include <string>
using namespace std;
struct node
{
	int p,a;
}x[5050];
bool cmp(node n1,node n2)
{
	return n1.p<n2.p;
}
int main () {
	int a,n;
	cin>>a>>n;
	int ans=0;
	for(int i=1;i<=n;i++)
	{
		cin>>x[i].p>>x[i].a;
	}
	sort(x+1,x+n+1,cmp);
	for(int i=1;i<=n;i++)
	{
		a-=x[i].a;
		ans+=x[i].p;
	}
	cout<<ans*20+10;
	return 0;
}

大佬们帮我看看哪里错了