#include <bits/stdc++.h>
#define mp make_pair
#define pb push_back
#define pf push_front
#define popb pop_back
#define popf pop_front
#define xx first
#define yy second
#define srt(a) sort(a.begin(),a.end());
#define srtg(a,int) sort(a.begin(),a.end(),greater<int>())
#define lb(a,x) lower_bound(a.begin(),a.end(),x)
#define up(a,x) upper_bound(a.begin(),a.end(),x)
#define fnd(a,x) find(a.begin(),a.end(),x)
#define vstart auto startt=chrono::system_clock::now()
#define vend auto endd=chrono::system_clock::now()
#define vvreme chrono::duration<double> vremee=endd-startt
#define ios ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0)
using namespace std;
typedef long long ll;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;
typedef string str;
const int maxn=5e5+10;
pll niz[maxn];
void solve(){
int n;
cin>>n;
for(int i=0;i<n;i++) cin>>niz[i].xx>>niz[i].yy;
sort(niz,niz+n);
ll res=0;
ll maxi=LLONG_MIN;
ll pref=0;
for(int i=0;i<n;i++){
maxi=max(maxi,-pref+niz[i].xx);
pref+=niz[i].yy;
res=max(res,pref+maxi-niz[i].xx);
}
cout<<res;
}
int main(){
ios;
int t=1;
//cin>>t;
while(t--) solve();
return 0;
}
