#include<bits/stdc++.h> //:3
using namespace std;
typedef long long ll;
#define all(a) (a).begin(), (a).end()
#define ff first
#define ss second
#define pb push_back
#define mp make_pair
#define pi pair<int, int>
#define sz(x) (int)((x).size())
#define int long long
const int dx[] = {0, 1, 0, -1};
const int dy[] = {1, 0, -1, 0};
const ll inf = 2e9;
const ll mod = 1e9 + 7;
const int N = 2e6 + 11;
const int X = 1e6;
const ll INF64 = 3e18 + 1;
const double eps = 1e-14;
const double PI = acos(-1);
//ifstream in(".in");
//ofstream out(".out");
int n, m, s[N];
struct yes{
int a, b;
};
yes t[N];
void solve(){
cin >> n;
for(int i = 1; i <= n; i++){
cin >> t[i].a >> t[i].b;
}
sort(t + 1, t + n + 1, [](yes l, yes r){
if(l.a != r.a)return (l.a < r.a);
return (l.b < r.b);
});
for(int i = 1; i <= n; i++){
s[i] = s[i - 1] + t[i].b;
}
int best = -INF64, ans = -INF64;
for(int i = 1; i <= n; i++){
best = max(best, t[i].a - s[i - 1]);
ans = max(ans, s[i] - t[i].a + best);
}
cout << ans << '\n';
}
int32_t main(){
ios_base :: sync_with_stdio(0); cin.tie(0); cout.tie(0);
cout << setprecision(6) << fixed;
int T = 1;
//cin >> T;
while(T--){
solve();
}
}
