#include<bits/stdc++.h>
#define int long long
using namespace std;
int a[500005], b[500005];
signed main()
{
ios_base::sync_with_stdio(false);
cin.tie(0);
int n; cin>>n;
vector<pair<int, int>> c(n);
for(int i = 0; i < n; i++) cin>>c[i].first>>c[i].second;
sort(c.begin(), c.end());
for(int i = 0; i < n; i++){
a[i+1] = c[i].first; b[i+1] = c[i].second;
}
for(int i = 1; i <= n; i++) b[i] += b[i-1];
int maximum = -1e18, ans = -1e18;
for(int i = 1; i <= n; i++){
maximum = max(maximum, -b[i-1] + a[i]);
ans = max(ans, b[i] - a[i] + maximum);
}
cout<<ans;
}
