#include <bits/stdc++.h>
#define endl "\n"
#define int long long
#define fir first
#define sec second
using namespace std;
signed main() {
ios::sync_with_stdio(false);
cin.tie(nullptr);
cout.tie(nullptr);
int n;
cin >> n;
vector<pair<int, int>> arts(n);
int sm = 0;
for (auto &x : arts) {
cin >> x.fir >> x.sec;
sm += x.sec;
}
sort(arts.begin(), arts.end());
int bl = -(int) 1e18, br = (int) 1e18;
int sml = 0, smr = 0;
vector<int> fl, fr;
for (int i = 0; i < n; i++) {
bl = max(bl, arts[i].fir - sml);
fl.push_back(bl);
sml += arts[i].sec;
}
for (int i = n - 1; i >= 0; i--) {
br = min(br, arts[i].fir + smr);
fr.push_back(br);
smr += arts[i].sec;
}
reverse(fr.begin(), fr.end());
int res = -(int) 1e18;
for (int i = 0; i < n; i++) {
res = max(res, sm + fl[i] - fr[i]);
}
cout << res << endl;
}
