#include <bits/stdc++.h>
#define int long long
#define moony long long
#define pii pair<int, int>
#define fi first
#define se second
#define ld long double
#define vi vector<int>
#define vii vector<vector<int>>
#define all(v) (v).begin(), (v).end()
#define rep(i, a, b) for (int i = (a), _b = (b); i <= _b; ++i)
#define per(i, b, a) for (int i = (b), _a = (a); i >= _a; --i)
using namespace std;
const int MOD = 1e9 + 7;
int add(int a, int b) {
a += b;
if (a >= MOD) a -= MOD;
return a;
}
int mul(int a, int b) {
(a *= b) %= MOD;
return a;
}
int ceil(int x, int y) {
return (x + y - 1) / y;
}
int bin_pow(int x, int y) {
int res=1;
while(y){if(y&1)res=res*x%MOD;x=x*x%MOD;y>>=1;}
return res;
}
const int INF = 1e17;
const int maxn = 1e6 + 5;
int pref[maxn + 5];
int calc(int l, int r) {
if (l > r) return 0;
if (!l) return pref[r];
return pref[r] - pref[l - 1];
}
void solve(int tc) {
int n; cin >> n;
vector<pair<int, int>> a(n);
for (int i = 0; i < n; ++i) cin >> a[i].first >> a[i].second;
sort(a.begin(), a.end());
for (int i = 0; i < n; ++i) {
if (!i) pref[0] = a[0].second;
else pref[i] = pref[i - 1] + a[i].second;
}
vector<int> orz(n);
for (int i = 0; i < n; ++i)
orz[i] = a[i].first + calc(i, n - 1);
int sum = -INF, ans = 0;
for (int i = 0; i < n; ++i) {
sum = max(sum, orz[i]);
ans = max(ans, sum - calc(i + 1, n - 1) - a[i].first);
}
cout << ans << '\n';
}
signed main() {
ios_base::sync_with_stdio(false);
cin.tie(0); cout.tie(0);
int tc = 1;
//cin >> tc;
for (int i = 1; i <= tc; ++i) {
solve(i);
}
}
