#include<bits/stdc++.h>
using namespace std;
#define fast ios_base::sync_with_stdio(false); cin.tie(NULL); cout.tie(NULL);
#define ll long long int
const ll N = 100+5 , INF = 1e18 , MOD = 1e9+7;
void solve(){
ll n;
cin >> n;
vector<pair<ll,ll>> a(n+5);
for(ll i = 1; i <= n; i++) cin >> a[i].first >> a[i].second;
sort(a.begin()+1,a.begin()+n+1);
ll mini = INF , ans = -INF , sum = 0;
for(ll i = 1; i <= n; i++){
mini = min(mini,sum-a[i].first);
sum += a[i].second;
ans = max(ans,sum-a[i].first-mini);
}
cout << ans;
}
int main(){
fast;
ll tc = 1;
// cin >> tc;
while(tc--) solve();
return 0;
}
