#include <bits/stdc++.h>
#define int long long
#define f first
#define s second
using namespace std;
int32_t main()
{
ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
int N; cin >> N;
vector<pair<int,int>> arr(N);
for(int i = 0;i<N;++i) cin >> arr[i].f >> arr[i].s; //size, value
sort(arr.begin(),arr.end());
vector<int> pref(N+1); pref[0] = 0;
for(int i = 1;i<=N;++i){
pref[i] = pref[i-1]+arr[i-1].s;
}
int cur = pref[0]-arr[0].f, ans = 0;
for(int i = 1;i<N;++i){
int x = pref[i]-arr[i].f;
cur = min(cur,x);
ans = max(ans,x-cur+arr[i].s);
//cout << cur << " " << x << "\n";
}
cout << ans << "\n";
return 0;
}
