#include <bits/stdc++.h>
using namespace std;
#define int long long
#define ll long long
#define pii pair <int, int>
#define pb push_back
#define mp make_pair
#define dbg puts("dbg");
#define outp(x) cout << #x << " = " << (x) << endl
#define all(x) (x).begin(), (x).end()
#define test int t; cin >> t; while(t--){solve();}
#define MOD 998244353
int fpb(int a,int b){if(b == 0){return a;}return fpb(b, a%b);}
int kpk(int a,int b){return (a*b)/fpb(a, b);}
int n, pref[500003];
pii art[500003];
// i ... j
// psum[j] - psum[i-1] - a[j] + a[i]
// psum[j] - a[j] + a[i] - psum[i-1]
void solve(){
cin >> n;
for(int i=1; i<=n; i++){
cin >> art[i].first >> art[i].second;
}
sort(art+1, art+n+1);
for(int i=1; i<=n; i++){
pref[i] = pref[i-1] + art[i].second;
}
int maxi = -2e18, ans = 0;
for(int i=1; i<=n; i++){
maxi = max(maxi, art[i].first - pref[i-1]);
ans = max(ans, maxi + pref[i] - art[i].first);
}
cout << ans << endl;
}
int32_t main() {
ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
solve();
return 0;
}
