#include <bits/stdc++.h>
using namespace std;
#define int long long
#define pb push_back
#define ins insert
#define all(x) x.begin(), x.end()
#define F first
#define S second
const int N = 200100, k = 350;
void solve(){
int n;
cin>>n;
vector<pair<int, int>>v(n);
for(int i = 0; i < n; i++){
cin>>v[i].F>>v[i].S;
}
sort(all(v));
int mx = -1e18;
int cur = 0;
int ans = 0;
for(int i = 0; i < n; i++){
mx = max(mx, v[i].F - cur);
cur += v[i].S;
ans = max(ans, cur - v[i].F + mx);
}
cout<<ans;
}
signed main(){
ios_base :: sync_with_stdio(false);
cin.tie(nullptr);
cout.tie(nullptr);
int t = 1;
//cin>>t;
while(t--){
solve();
}
}
