#define _USE_MATH_DEFINES 1
#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace std;
using namespace __gnu_pbds;
#define MOD 1000000007ll
#define INF 1000000000000000000ll
#define EPS 1e-9
#define getchar_unlocked _getchar_nolock
#define putchar_unlocked _putchar_nolock
typedef long long ll;
typedef long double ld;
typedef pair <ll,ll> pl;
typedef tuple <ll,ll,ll> tl;
ll TC, N, P[500005], R, M;
vector <pl> art;
int main() {
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
TC = 1;
for (ll tc = 1; tc <= TC; tc++) {
cin >> N;
art.emplace_back(0, 0);
for (ll i = 1; i <= N; i++) {
ll a, b;
cin >> a >> b;
art.emplace_back(a, b);
}
sort(art.begin(), art.end());
P[0] = 0;
for (ll i = 1; i <= N; i++) {
P[i] = P[i-1] + art[i].second;
}
M = 0;
R = INF;
for (ll i = 1; i <= N; i++) {
R = min(R, P[i-1] - art[i].first);
M = max(M, P[i] - art[i].first - R);
}
cout << M << "\n";
}
return 0;
}
