#include <bits/stdc++.h>
using namespace std;
#define endl '\n'
#define fi first
#define se second
#define For(i, l, r) for (auto i = (l); i < (r); i++)
#define ForE(i, l, r) for (auto i = (l); i <= (r); i++)
#define FordE(i, l, r) for (auto i = (l); i >= (r); i--)
#define Fora(v, a) for (auto v: (a))
#define bend(a) (a).begin(), (a).end()
#define isz(a) ((signed)(a).size())
using ll = long long;
using ld = long double;
using pii = pair <int, int>;
using vi = vector <int>;
using vpii = vector <pii>;
using vvi = vector <vi>;
const int N = 5e5 + 5;
int n;
pair <ll, int> a[N];
ll b[N];
ll c[N];
signed main(){
ios_base::sync_with_stdio(0);
cin.tie(0); cout.tie(0);
// freopen("KEK.inp", "r", stdin);
// freopen("KEK.out", "w", stdout);
cin >> n;
ForE(i, 1, n){
cin >> a[i].fi >> a[i].se;
}
sort(a + 1, a + n + 1);
ForE(i, 1, n){
b[i] = b[i - 1] + a[i].se;
}
ll ans = 0, val = numeric_limits <ll>::min();
ForE(i, 1, n){
val = max(val, a[i].fi - b[i - 1]);
ans = max(ans, b[i] - a[i].fi + val);
}
cout << ans << endl;
}
/*
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INPUT |
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OUTPUT |
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*/
