#include <bits/stdc++.h>
#define int long long
#define fi first
#define se second
using namespace std;
pair<int, int> a[500001];
int dp[500002];
signed main(){
ios_base::sync_with_stdio(0);
cin.tie(0);
int n;
cin >> n;
for (int i = 1;i<=n;++i){
cin >> a[i].fi >> a[i].se;
}
sort(a+1, a+n+1);
dp[0] = 0;
for (int i = 1;i<=n;++i){
dp[i] = dp[i-1] + a[i].se;
}
int res = 0;
set<int> se;
for (int i = 1;i<=n;++i){
se.insert(a[i].fi - dp[i-1]);
int s = dp[i] - a[i].fi + a[1].fi;
auto it = prev(se.end());
res = max(res, s - a[1].fi + *it);
}
cout << res;
}
