#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
using namespace __gnu_pbds;
#ifdef lisie_bimbi
#else
#define endl '\n'
#endif
typedef long long ll;
const ll inf = 1'000'000'000'000'000'000;
using namespace std;
#pragma GCC optimize("O3")
#pragma GCC target("avx,avx2,bmi2,fma,popcnt")
#define int long long
void solve(){
int n;
cin >> n;
vector<pair<int, int>> a(n);
for(int i = 0; i < n; i++){
cin >> a[i].first >> a[i].second;
}
std::sort(a.begin(), a.end());
vector<int> p(n + 1);
for(int i = 0; i < n; i++){
p[i + 1] = p[i] + a[i].second;
}
for(int i = 0; i < n; i++){
p[i] -= a[i].first;
}
int mn = inf;
int ans = 0;
for(int i = 0; i < n; i++){
mn = min(mn, p[i]);
int x = p[i + 1] - a[i].first;
if(i + 1 < n){
x += a[i + 1].first;
}
ans = max(ans, x - mn);
}
cout << ans << endl;
}
signed main(){
#ifdef lisie_bimbi
freopen("input.txt", "r", stdin);
freopen("output.txt", "w", stdout);
#else
cin.tie(nullptr)->sync_with_stdio(false);
#endif
cout << setprecision(5) << fixed;
int _ = 1;
//cin >> t;
while(_--){
solve();
}
return 0;
}
