不知道为什么通不过去，7910RE 8WA

# include <cstdio>
# include <algorithm>
# include <cmath>
using namespace std;
long long n,l[10010],r[10010],pos,ans;
int main()
{
	scanf("%d", &n);
	for (int i=1;i<=n;i++)
	{
		scanf("%lld%lld", &l[i],&pos);
		r[i]=l[i]-pos,l[i]=pos;
		if (l[i]<r[i]) swap(l[i],r[i]);
	}
	sort(l+1,l+n+1);
	sort(r+1,r+n+1);
	if (n==1)
	{
		printf("%d", l[1]+r[1]);
	}
	if (r[n]>l[n-1]) ans = r[n]+l[n];
	else ans = l[n]+l[n-1];
	printf("%lld", ans);
	return 0;
}