#include <bits/stdc++.h>
using namespace std;
#define int long long
#define endl "\n"
#define pb push_back
#define ff first
#define ss second
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
void solve(){
int n; cin >> n;
vector<pair<int,int>> v(n);
for(auto &[x,y] : v){
cin >> x >> y;
}
int maxi = 0,sum = 0,ans = 0; sort(all(v));
for(int i = 0; i < n; i++){
maxi = max(maxi,v[i].ff - sum);
sum = sum + v[i].ss;
ans = max(ans,maxi + sum - v[i].ff);
}
cout << ans << endl;
}
signed main(){
ios::sync_with_stdio(0);
cin.tie(0);
int t = 1;
// cin >> t;
while(t--)
solve();
return 0;
}
