#include<bits/stdc++.h>
using namespace std;
#define int long long
#define fi first
#define se second
#define pb push_back
typedef pair<int, int> ii;
typedef pair<ii, int> iii;
typedef pair<ii, ii> iiii;
const int N = 6e5 + 5;
const int mod = 1e9 + 7, oo = 1e18 + 7;
int n;
ii arr[N];
void process(){
cin >> n;
for(int i = 1; i <= n; i++){
cin >> arr[i].fi >> arr[i].se;
}
sort(arr + 1, arr + n + 1);
int mini = 0, pref = 0, answer = -oo;
for(int i = 1; i <= n; i++){
pref += arr[i].se;
//cout << pref << " " << arr[i].fi << " " << mini << '\n';
answer = max(answer, (pref - arr[i].fi - mini));
mini = min(mini, (pref - arr[i].se) - arr[i].fi);
}
cout << answer << "\n";
}
signed main(){
ios_base::sync_with_stdio(0);
//freopen("KEK.inp", "r", stdin);
//freopen("KEK.out", "w", stdout);
cin.tie(0);
process();
}
