#include <bits/stdc++.h>
using namespace std;
using ll = long long;
const int N = 5e+5;
const ll INF = LLONG_MAX/2;
int n;
vector<pair<ll,int>> vec;
ll a[N], qs[N];
int main()
{
ios_base::sync_with_stdio(0); cin.tie(0);
cin >> n;
vec.resize(n);
for( auto &[a, b] : vec ) cin >> a >> b;
sort( vec.begin(), vec.end() );
for( int i=1;i<=n;i++ )
{
a[i] = vec[i-1].first;
qs[i] = qs[i-1]+vec[i-1].second;
//cout << a[i] << " " << qs[i] << endl;
}
ll ans = 0, mx = -INF;
for( int i=1;i<=n;i++ )
{
mx = max( mx, a[i]-qs[i-1] );
ans = max( ans, -a[i]+qs[i]+mx );
//cout << "mx " << mx << " ans " << ans << endl;
}
cout << ans;
}
