#include <bits/stdc++.h>
#define nl '\n'
const int mxN = 5e5 + 5;
int N;
std::pair<int64_t, int64_t> a[mxN];
int64_t pref[mxN];
signed main() {
std::ios::sync_with_stdio(false);
std::cin.tie(nullptr);
std::cin >> N;
for (int i = 0; i < N; i++) {
std::cin >> a[i].first >> a[i].second;
}
std::sort(a, a + N);
/*
*/
for (int i = 0; i < N; i++) {
pref[i + 1] = pref[i] + a[i].second;
}
// maximize pref[i + 1] - pref[j] - (a[i].first - a[j].second)
// pref[i + 1] - a[i].first - pref[j] + a[j].second
int64_t maximal = -1e18;
int64_t ans = maximal;
for (int i = 0; i < N; i++) {
maximal = std::max(maximal, a[i].first - pref[i]);
ans = std::max(ans, pref[i + 1] - a[i].first + maximal);
}
std::cout << ans << nl;
}
