#include<bits/stdc++.h>
#define int long long
#define fi first
#define se second
using namespace std;
int const MOD = 1e9 + 7, N = 5e5 + 5;
int n, val[N], luu[N];
pair<int, int> a[N];
signed main() {
cin.tie(0)->sync_with_stdio(0);
cin >> n;
for(int i = 1; i <= n; i++) cin >> a[i].fi >> a[i].se;
sort(a + 1, a + n + 1);
val[1] = a[1].se;
luu[1] = val[1] - a[1].fi;
for(int i = 2; i <= n; i++){
val[i] = val[i - 1] + a[i].se;
//luu[i] = val[i] - a[i].fi;
}
//sort(luu + 1, luu + n + 1);
//cout << luu[n] + luu[n - 1];
// (val[r] - val[l - 1]) - a[r].fi + a[l].fi
// (val[r] - a[r].fi) + (a[l].fi - val[l - 1])
int ma = -1e18, res = -1e18;
for(int i = 1; i <= n; i ++) {
ma = max(ma, a[i].fi - val[i - 1]);
res = max(res, ma + val[i] - a[i].fi);
}
cout << res;
}
