#include <bits/stdc++.h>
using namespace std;
#define int long long
signed main() {
ios_base::sync_with_stdio(false);
cin.tie(NULL);
cout.tie(NULL);
int n;
cin >> n;
vector<pair<int, int>> v(n + 1);
for(int i = 1; i <= n; i++){
cin >> v[i].first >> v[i].second;
}
sort(v.begin(), v.end());
int p[n + 1];
p[0] = 0;
for(int i = 1; i <= n; i++){
p[i] = p[i - 1] + v[i].second;
}
int ans1 = -1;
int ans2 = LLONG_MAX;
for(int i = 1; i < n; i++){
ans1 = max(ans1, p[i] - v[i].first);
ans2 = min(ans2, p[i - 1] - v[i].first);
}
cout << ans1 - ans2;
return 0;
}
