#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define ar array
const int mxN = 2e5+1, M = 1e9+7;
int main(){
#ifdef _DEBUG
// freopen("input.txt", "r", stdin);
// freopen("output.txt", "w", stdout);
#endif
std::ios_base::sync_with_stdio(false); std::cin.tie(0); std::cout.tie(0);
int n;
cin >> n;
vector<pair<ll, ll>> a(n+1);
for(int i = 1; i<=n; ++i){
cin >> a[i].first >> a[i].second;
}
sort(a.begin(), a.end());
for(int i = 1; i<=n; ++i){
a[i].second += a[i-1].second;
}
ll mx = -1e18, ans = 0;
for(int i = 1; i<=n; ++i){
mx = max(mx, a[i].first - a[i-1].second);
ans = max(ans, -a[i].first + a[i].second + mx);
}
cout << ans << "\n";
}
