#include <bits/stdc++.h>
using namespace std;
#define int long long
typedef pair<int, int> ii;
signed main() {
int n = 0;
cin >> n;
vector<ii> art(n, ii(0, 0));
for (int i = 0; i < n; ++i) {
cin >> art[i].first >> art[i].second;
}
sort(art.begin(), art.end());
vector<int> prefixval(n, 0);
prefixval[0] = art[0].second;
for (int i = 1; i < n; ++i) {
prefixval[i] = prefixval[i - 1] + art[i].second;
}
int l = 0, maxval = 0, val = 0;
for (int i = 0; i < n; ++i) {
if (l == 0) {
val = prefixval[i] - art[i].first + art[l].first;
} else {
val = prefixval[i] - prefixval[l - 1] - art[i].first + art[l].first;
}
while (val < 0) {
l++;
val = prefixval[i] - prefixval[l - 1] - art[i].first + art[l].first;
}
maxval = max(maxval, val);
}
cout << maxval << '\n';
return 0;
}
