#include <bits/stdc++.h>
#define pii pair<ll, ll>
typedef long long ll;
using namespace std;
const int MAX = 500005;
pii P[MAX];
ll dp[MAX];
int main() {
ios::sync_with_stdio(0); cin.tie(0);
int N;
cin >> N;
for (int i = 1; i <= N; ++i) {
ll a, b;
cin >> a >> b;
P[i] = { a, b };
}
sort(P, P + N + 1);
ll cur = 0, ans = 0;
for (int i = N; i > 0; --i) {
cur += P[i].second - P[i].first + P[i - 1].first;
dp[i] = cur;
cur = max(0LL, cur);
}
for (int i = 1; i <= N; ++i) {
ans = max(ans, max(P[i].second, P[i].second + dp[i + 1]));
}
cout << ans;
return 0;
}
