#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define pll pair<ll, ll>
#define F first
#define S second
const int maxn = 5e5 + 5;
const ll inf = 9e18;
int n;
pll arr[maxn];
ll qs[maxn];
ll mn = inf, res = -inf;
int main(){
ios_base::sync_with_stdio(0);cin.tie(0);
cin >> n;
for(int i=1;i<=n;++i){
cin >> arr[i].F >> arr[i].S;
}
sort(arr+1, arr+1+n);
for(int i=1;i<=n;++i) qs[i] = qs[i-1] + arr[i].S;
for(int i=1;i<=n;++i){
mn = min(mn, qs[i-1] - arr[i].F);
res = max(res, qs[i] - arr[i].F - mn);
}
cout << res;
}
