#include<bits/stdc++.h>
#define fi first
#define se second
#define int long long
using namespace std;
using ll = long long;
using ii = pair<int, int>;
using aa = array<int,3>;
const int N = 5e5+5;
int n, ans = -1e18;
int suf[N];
ii a[N];
signed main(){
ios_base::sync_with_stdio(false);
cin.tie(NULL);cout.tie(NULL);
cin >> n;
for (int i = 1; i <= n; i++){
cin >> a[i].fi >> a[i].se;
}
sort(a+1,a+1+n);
int cur = 0;
suf[n + 1] = -1e18;
for (int i = n; i >= 1; i--){
suf[i] = max(suf[i + 1],- cur - a[i].fi);
cur += a[i].se;
ans = max({ans,suf[i + 1] + a[i].fi + cur, a[i].se});
}
cout << ans;
return 0;
}
