#include <bits/stdc++.h>
using namespace std;
#define int long long
// #define endl '\n'
#define ff first
#define ss second
#define pb push_back
#define all(a) a.begin(), a.end()
#define rall(a) a.rbegin(), a.rend()
#define ar array
const int MOD = 1e9 + 7,INF = 1e18, N = 2e5 + 5;
/*
*/
int ans = 0;
void solve(){
int n;
cin >> n;
vector <pair<int,int>> a(n);
vector <int> sum(n);
for(int i = 0;i < n;i++){
cin >> a[i].ff >> a[i].ss;
}
sort(all(a));
sum[0] = a[0].ss;
for(int i = 1;i < n;i++){
sum[i] = sum[i - 1] + a[i].ss;
}
vector <int> dp(n);
dp[n - 1] = sum[n - 1] - a[n - 1].ff;
for(int i = n - 2;i >= 0;i--){
dp[i] = max(dp[i + 1] , sum[i] - a[i].ff);
}
int h = 0;
for(int i = 0;i < n;i++){
ans = max(dp[i] + a[i].ff - h, ans);
h += a[i].ss;
}
// for(int i = 0;i < n;i++){
// cout<< dp[i]<< ' ';
// }
// cout<<endl;
cout<<ans<<endl;
}
signed main() {
ios::sync_with_stdio(false);
cin.tie(nullptr);
int ti = 1;
while (ti--) {
solve();
}
}
