#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const ll INF=1e18+27092008;
const int N=5e5+5;
template<class T>
bool maximize(T &a, const T &b) {
if (a < b) return a = b, 1;
return 0;
}
int n;
pair<ll,ll> a[N];
void init(){
cin>>n;
for(int i=1;i<=n;i++) cin >> a[i].first >> a[i].second;
}
void solve(){
init();
sort(a+1,a+n+1);
ll best = -INF, ans = -INF;
for(int i=1;i<=n;i++) {
a[i].second += a[i-1].second;
maximize(best, -a[i-1].second+a[i].first);
maximize(ans,a[i].second-a[i].first+best);
}
cout<<ans;
}
signed main(){
ios_base::sync_with_stdio(0);cin.tie(0); cout.tie(0);
solve();
return 0;
}
