#include <iostream>
#include <vector>
#include <algorithm>
#include <numeric>
#include <cassert>
#include <queue>
using namespace std;
using ll = long long;
#define int ll
#define fore(a, b, c) for(int a=b; a<c; ++a)
#define sz(x) (int) x.size()
#define all(x) x.begin(), x.end()
#define vi vector<int>
#define ii pair<int,int>
#define F first
#define S second
const int MAXN = 5050;
int n;
ii arr[MAXN];
int sum[MAXN];
int as[MAXN];
signed main(){
ios::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
cin >> n;
fore(i, 0, n){
cin >> arr[i].F >> arr[i].S;
}
sort(arr, arr+n, [](ii u, ii v) -> bool {
if(u.F == v.F){
return u.S < v.S;
}
return u.F < v.F;
});
fore(i, 0, n){
as[i] = arr[i].F;
}
fore(i, 0, n){
sum[i+1] = sum[i] + arr[i].S;
}
int ans = 0;
fore(i, 0, n){
fore(j, i, n){
int res = sum[j+1] - sum[i];
res -= as[j] - as[i];
ans = max(ans, res);
}
}
cout << ans;
}
