///huynhocute123///
#include<bits/stdc++.h>
using namespace std;
#define S second
#define F first
#define pii pair<int,int>
#define piii pair<int,pair<int,int>>
#define pb push_back
#define FOR(i, a, b) for(int i = a; i <= b; ++i)
#define REP(i, a, b) for(int i = b; i >= a; --i)
#define ALL(v) v.begin(),v.end()
#define inp(name) if(fopen(name, "r")) freopen(name, "r", stdin);
#define out(name) if(fopen(name, "w")) freopen(name, "w", stdout);
//random_device rd;
//mt19937 rng(rd());
//#pragma GCC optimize ("O3")
//#pragma GCC optimize ("unroll-loops")
//#pragma GCC target("popcnt")
//#define int long long
const int MAX = 1e9+9;
const long long MAXLL = 1e18+9;
const double pi = 3.14159265358979323846;
const double rad = 3.14159265358979323846 /180;
bool minimize(int &u, int v){
if(v < u){
u = v;
return 1;
}
return 0;
}
bool maximize(int &u, int v){
if(v > u){
u = v;
return 1;
}
return 0;
}
bool maximizell(long long &u, long long v){
if(v > u){
u = v;
return 1;
}
return 0;
}
bool minimizell(long long &u, long long v){
if(v < u){
u = v;
return 1;
}
return 0;
}
const int mod = 1e9 + 7;
inline int fastPow(int a, int n){
if(n == 0) return 1;
int t = fastPow(a, n >> 1);
t = 1ll * t * t % mod;
if(n & 1) t = 1ll * t * a % mod;
return t;
}
const int maxN =5 * 1e5 + 999 ;
int n;
struct art{
long long Size ,Value;
bool operator < (const art& rhs)const{
return Size < rhs.Size;
}
}Art[maxN];
long long pref[maxN];
inline void solve(){
cin >> n;
FOR(i, 1, n)cin >> Art[i].Size >> Art[i].Value;
sort(Art + 1, Art + 1 + n);
long long res = -MAXLL;
FOR(i, 1, n)pref[i] = pref[i - 1] + Art[i].Value;
long long kk = -MAXLL;
REP(i , 1, n){
maximizell(kk , pref[i] - Art[i].Size);
maximizell(res, kk - pref[i - 1] + Art[i].Size);
}
cout << res ;
}
signed main(){
ios_base::sync_with_stdio(false);
cin.tie(0);
#define NAME "task"
if(fopen(NAME".inp", "r")){
freopen(NAME".inp", "r" ,stdin);
// freopen(NAME".out", "w" ,stdout);
}
int tc = 1;
// cin >> tc;
while( tc-- )solve();
cerr << '\n' << "Time elapsed: " << (1.0 * clock() / CLOCKS_PER_SEC) << " s\n" ;
}
