#include <bits/stdc++.h>
#define ll long long
#define f first
#define s second
#define pii pair<int,int>
#define pll pair<ll,ll>
#define pb push_back
#define epb emplace_back
#define ull unsigned ll
using namespace std;
int main(){
int n; cin >> n;
pll a[n + 1];
for(int i= 1; i <= n; i++) cin >> a[i].f >> a[i].s;
sort(a + 1, a + 1 + n);
ll pref[n + 1];
pref[0] = 0;
for(int i = 1; i <= n; i++) pref[i] = pref[i - 1] + a[i].s;
ll mx = 0;
ll ans = 0;
for(int i = 1; i <= n; i++){
mx = max(mx, a[i].f - pref[i - 1]);
ans = max(ans, pref[i] - a[i].f + mx);
}
cout << ans;
return 0;
}
