#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define arr array
#define vec vector
#define sz(a) ((int)(a).size())
void p2() {
/*
2 3 ->
4 5 -> 4
11 2 -> 0
*/
int N;
cin >> N;
vector<arr<ll, 2>> AB(N);
// arr<int, 2> AB[N];
for(int i = 0; i < N; i++) {
cin >> AB[i][0] >> AB[i][1];
}
sort(AB.begin(), AB.end());
ll pref[N + 1];
pref[0] = 0;
for(int i = 1; i <= N; i++) {
pref[i] = pref[i - 1] + AB[i - 1][1];
}
ll sufmax[N + 2];
sufmax[N + 1] = -9e18;
for(int i = N; i >= 1; i--) {
sufmax[i] = max(sufmax[i + 1], pref[i] - AB[i - 1][0]);
}
ll ans = -9e18;
for(int i = 1; i <= N; i++) {
ans = max(ans, sufmax[i] - pref[i - 1] + AB[i - 1][0]);
}
cout << ans << endl;
}
int main() {
p2();
}
