#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define pll pair<ll, ll>
#define pii pair<int, int>
#define fs first
#define sc second
#define pb push_back
void solve() {
int n;
cin>>n;
pll a[n];
for(int i=0;i<n;i++)cin>>a[i].fs>>a[i].sc;
sort(a,a+n);
ll p=0,x=-1e18,ans=0;
for(int i=0;i<n;i++){
x=max(x,a[i].fs-p);
p+=a[i].sc;
ans=max(ans,p-a[i].fs+x);
}
cout<<ans<<'\n';
}
int main() {
#ifdef FPO
freopen("in","r",stdin);
freopen("out","w",stdout);
#endif
ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
solve();
}
