#pragma GCC optimize("Ofast")
#include <bits/stdc++.h>
using namespace std;
#define endl "\n"
#define creeper_bonc ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
#define pb push_back
#define fi first
#define se second
#define pii pair<int, int>
#define all(v) (v).begin(), (v).end()
#define ins insert
#define nl endl
//#define int long long
const int imax = INT_MAX;
const int imin = INT_MIN;
void _()
{
int n; cin>>n;
vector <pii> v;
for(int i = 0;i < n;i++) cin>>v[i].fi>>v[i].se;
sort(all(v));
int mx = imin, sum = 0, mx1 = imin;
for(int i = 0;i < n;i++)
{
sum += v[i].se;
mx1 = max(mx1, v[i].fi - (sum - v[i].se));
mx = max(mx, sum - v[i].fi + mx1);
}
cout<<mx;
}
signed main()
{
creeper_bonc
int t=1;
//cin>>t;
while(t--) {
_();
cout<<endl;}
}
/*Author: Davud*/
