#pragma GCC optimize("O3,unroll-loops")
#pragma GCC target("avx2,bmi,bmi2,lzcnt,popcnt")
#include <bits/stdc++.h>
using namespace std;
#define db long double
#define ll long long
#define pii pair<int, int>
#define pll pair<ll, ll>
#define vi vector<int>
#define vl vector<ll>
#define vii vector<pii>
#define vll vector<pll>
#define endl '\n'
#define all(x) x.begin(), x.end()
#define fastio\
ios_base::sync_with_stdio(0);\
cin.tie(0);\
cout.tie(0)\
#define int long long
const int sz = 5e5 + 5;
int n, pre;
pii a[sz];
signed main(){
cin >> n;
for(int i = 1; i <= n; i++){
cin >> a[i].first >> a[i].second;
}
sort(a + 1, a + n + 1);
int res = -1e18, s = 0;
for(int i = 1; i <= n; i++){
pre = max(pre, a[i].first - s);
s += a[i].second;
res = max(res, s + pre - a[i].first);
}
cout << res;
}
