#include <bits/stdc++.h>
using namespace std;
const long long inf = (long long)1e18;
int main() {
ios::sync_with_stdio(false);
cin.tie(0);
int n;
cin >> n;
vector<pair<long long , long long>> a(n);
for (int i = 0 ; i < n ; i++) {
cin >> a[i].first >> a[i].second;
}
sort(a.rbegin() , a.rend());
vector<long long> dp(n);
long long ans = 0;
for (int i = 0 ; i < n ; i++) {
dp[i] = a[i].second - a[i].first;
if (i > 0) dp[i] = max(dp[i] , dp[i - 1] + a[i].second);
ans = max(ans , dp[i] + a[i].first);
}
cout << ans << '\n';
return 0;
}
