30大分求条

#include<bits/stdc++.h>
using namespace std;
int a[100025],b[100025];
int main(){
	//freopen("bamboo.in","r",stdin);
	//freopen("bamboo.out","w",stdout);
	int n;
	scanf("%d%d%d",&n,&a[0],&b[0]);
	long long lmx=0,rmx=0,ans;
	for(register int i=1;i<n;++i){
		scanf("%d%d",&a[i],&b[i]);
		long long mx1=max(b[i-1],a[i-1]-b[i-1]),mx2=max(b[i],a[i]-b[i]);
		long long mn1=a[i-1]-mx1,mn2=a[i]-mx2;
		//int lft=max(mx1,mn2),rht=max(mx2,mn1);
		lmx=max(lmx,max(mx1,mn2));
		rmx=max(rmx,max(mx2,mn1));
		ans=lmx+rmx;
	}
	cout<<ans;
	return 0;
}