#include <bits/stdc++.h>
#define endl '\n'
#define all(v) v.begin(),v.end()
#define rall(v) v.rbegin(),v.rend()
#define F first
#define S second
#define pf push_front
#define pb push_back
#define ll long long
#define ull unsigned long long
#define ld long double
#define int long long
#define vi vector <int>
#define pii pair <int,int>
#define tiii tuple<int,int,int>
#define yes cout << "Yes" << endl
#define no cout << "No" << endl
#define YES cout << "YES" << endl
#define NO cout << "NO" << endl
#define out(v) for (auto x:v) cout << x << ' '
#define out1(v) for (auto x:v) cout << x << endl
#define inp(arr) for (int i=0;i<arr.size();i++) cin>>arr[i]
const int MAX=1e7+7;
const int MOD=1e9+7;
using namespace std;
const int inf=1e18;
int lejandr(int a,int b){
int sum=0;
while(a>0){
a/=b;
sum+=a;
}
return sum;
}
void solve(){
int n;
cin>>n;
vector<pii> vt(n);
for(int i=0;i<n;i++){
cin>>vt[i].F>>vt[i].S;
}
sort(all(vt));
int a=0,b=inf,c=0;
for(int i=0;i<n;i++){
b=min(b,a-vt[i].F);
a+=vt[i].S;
c=max(c,a-vt[i].F-b);
}
cout<<c<<endl;
}
signed main(){
ios_base::sync_with_stdio(0);
cin.tie(nullptr);
int t=1;
//cin>>t;
while(t--) {
solve();
}
}
