#include<deque>
#include<queue>
#include<vector>
#include<algorithm>
#include<iostream>
#include<set>
#include<cmath>
#include<tuple>
#include<string>
#include<chrono>
#include<functional>
#include<iterator>
#include<random>
#include<unordered_set>
#include<unordered_map>
#include<array>
#include<map>
#include<bitset>
#include<iomanip>
using namespace std;
typedef long long int llint;
typedef long double lldo;
#define mp make_pair
#define mt make_tuple
#define pub push_back
#define puf push_front
#define pob pop_back
#define pof pop_front
#define fir first
#define sec second
#define res resize
#define ins insert
#define era erase
#define RE return 0
//ios::sync_with_stdio(false);
//std::cin.tie(0);
//<< setprecision(20)
const int mod=1e9+7;
const llint big=1e15+100;
const long double pai=3.141592653589793238462643383279502884197;
const long double ena=2.71828182845904523536;
const long double eps=1e-7;
template <class T,class U>void mineq(T& a,U b){if(a>b){a=b;}}
template <class T,class U>void maxeq(T& a,U b){if(a<b){a=b;}}
template <class T> void soun(T& ar)
{sort(ar.begin(),ar.end());ar.erase(unique(ar.begin(),ar.end()),ar.end());}
int main(void){
	int n;cin>>n;
	llint ans=0,gen=0,mae=0;
	vector<pair<llint,llint>> ke(n);
	for(auto &it:ke){cin>>it.fir>>it.sec;}
	sort(ke.begin(),ke.end());
	for(auto it:ke){
		gen-=it.fir-mae;
		mae=it.fir;
		maxeq(gen,0);
		gen+=it.sec;
		maxeq(ans,gen);
	}
	cout<<ans<<endl;
	RE;
}