#include <bits/stdc++.h>
#pragma GCC optimize("Ofast")
#pragma GCC target("avx,avx2,fma")
using namespace std;
#define int long long
#define nl '\n'
#define io ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0)
const int mod = 1000000007, mod2 = 998244353;
// change this
const int N = 500005;
int n, ans, maxi;
pair<int, int> arr[N];
signed main() {
io;
cin >> n;
for (int i=0; i<n; i++) {
cin >> arr[i].first >> arr[i].second;
}
sort(arr, arr+n);
maxi = -1e18;
for (int i=n-1; i>=0; i--) {
maxi = max(maxi + arr[i].second, arr[i].second - arr[i].first);
ans = max(ans, maxi + arr[i].first);
}
cout << ans << nl;
}
