#include <bits/stdc++.h>
#include <climits>
using namespace std;
#define f first
#define s second
#define all(a) a.begin(),a.end()
#define sz(a) (int)a.size()
#define int long long
const int N=5e5+5;
int n;
pair<int,int> M[N];
int dp[N];
bool comp(pair<int,int>a,pair<int,int>b){
return a.f<b.f;
}
int pre[N];
void solve(){
cin>>n;
for(int i=1;i<=n;++i) cin>>M[i].f>>M[i].s;
sort(M+1,M+n+1,comp);
for(int i=1;i<=n;++i)pre[i]=pre[i-1]+M[i].s;
int best=0;
int ans=0;
for(int i=1;i<=n;++i){
best=max(best,M[i].f-pre[i-1]);
ans=max(ans,pre[i]-M[i].f+best);
}
cout<<ans;
}
signed main(){
ios_base::sync_with_stdio(0);cin.tie(0);
int T=1;
while(T--) solve();
}
