#include <bits/stdc++.h>
using namespace std;
#define N 1000005
#define int long long
const int inf = INT_MAX;
const int M = 998244353;
int n, p[N], sm[N], ans, sum;
pair <int,int> a[N];
signed main() {
ios::sync_with_stdio(0);cin.tie(0);
cin >> n;
for(int i = 1; i <= n; i++) {
cin >> a[i].first >> a[i].second;
}
sort(a + 1, a + n + 1);
sm[0] = 0;
int ans = 0;
for(int i = 1; i <= n; i++) {
sm[i] = sm[i - 1] + a[i].second;
for(int j = i - 1; j >= 1; j--) {
ans = max(ans, sm[i] - sm[j - 1] - a[i].first + a[j].first);
}
}
cout << ans << endl;
return 0;
}
