#include<bits/stdc++.h>
using namespace std;
#define int long long
int n,a[100100],b[100100];
bool cmp(int x,int y){
	return x>y;
}
signed main(){
	//freopen("bamboo.in","r",stdin);
	//freopen("bamboo.ans","w",stdout);
	cin>>n;
	for(int i=1;i<=n;i++){
		cin>>a[i]>>b[i];
		b[i]=max(b[i],a[i]-b[i]);
	}
	sort(b+1,b+1+n,cmp);
	cout<<b[1]+b[2];
	return 0;
}