#include <bits/stdc++.h>
using namespace std;
// #pragma GCC optimize("Ofast")
// #pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,avx2,fma")
// #pragma GCC optimize("unroll-loops")
#define ll long long
#define int128 __int128_t
#define pii pair<int, int>
#define int long long
#define pb push_back
#define F first
#define S second
#define all(v) (v).begin(), (v).end()
#define rall(v) (v).begin(), (v).end()
#define MOD 1000000007
#define INF (ll)1e18
#define RINF (ll) - 1e18
void cinv(vector<int> &a, int n){for (int i = 0; i < n; i++){cin >> a[i];}}
void coutv(vector<int> &a, int n){for (int i = 0; i < n; i++){cout << a[i] << " ";}}
void solve()
{
int n;
cin>>n;
vector<pair<int,int>>a;
vector<int>d;
a.push_back({0,0});
for(int i = 1;i<=n;i++){
int x,y;
cin>>x>>y;
a.push_back({x,y});
}
sort(a.begin(),a.end());
for(int i = 1;i<=n;i++){
a[i].S = a[i-1].S+a[i].S;
d.push_back(a[i-1].S-a[i].F);
}
int d1 = 0;
int h = 1e18;
for(int i = 1;i<=n;i++){
int g = a[i].S-a[i].F;
h = min(h,d[i-1]);
d1 = max(d1,g-h);
// cout<<d[i-1]<<" "<<g<<" "<<i<<" "<<a[i].F<<" "<<a[i].S<<endl;
}
cout<<d1<<endl;
}
signed main()
{
ios_base::sync_with_stdio(false);
cin.tie(NULL);
int t = 1;
// cin >> t;
while (t--)
{
solve();
}
}
