#include<bits/stdc++.h>
#define endl "\n"
#define int long long int
#define pb push_back
#define mp make_pair
#define Bound 2e5 + 1
#define mid (l+r+1)/2
using namespace std;
void solve() {
int n;
cin >> n;
int pre = 0;
int mn = 1e18+5;
int ans = 0;
array<int,2>* arr = new array<int,2>[n];
for(int i = 0; i < n; i++) cin >> arr[i][0] >> arr[i][1];
sort(arr, arr+n);
for(int i = 0; i < n; i++) {
mn = min(mn, pre-arr[i][0]); //If get a smaller mn, restart the exhibition form i
//difference = arr[i][0] - mn
pre = pre + arr[i][1]; //total point
ans = max(ans, pre - arr[i][0] - mn); //total point - difference
}
cout << ans;
}
int32_t main() {
cin.tie(0); cout.tie(0);
//ios::sync_with_stdio(false);
int t = 1; //cin >> t;
while(t--) solve();
return 0;
}
