#include <bits/stdc++.h>
using namespace std;
#define fi first
#define se second
#define mp make_pair
#define pb push_back
#define eb emplace_back
#define all(x) x.begin(), x.end()
typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, int> pli;
typedef pair<ll, ll> pll;
const int N = 5e5 + 3;
int n;
ll dp[N], pref[N];
pll a[N];
void solve() {
cin >> n;
for (int i = 1; i <= n; ++i)
cin >> a[i].fi >> a[i].se;
sort(a + 1, a + n + 1);
ll ans = 0;
for (int i = 1; i <= n; ++i) {
dp[i] = max(a[i].se, pref[i - 1] + a[i].se - a[i].fi);
ans = max(ans, dp[i]);
dp[i] += a[i].fi;
pref[i] = max(pref[i - 1], dp[i]);
}
cout << ans;
}
int main() {
cin.tie(NULL);
ios_base::sync_with_stdio(false);
solve();
return 0;
}
