#include <bits/stdc++.h>
using namespace std;
#define mod 1000000007
#define maxn 200005
#define f first
#define s second
#define ll long long
#define pb(x) push_back(x)
void solve(){
int n;
cin >> n;
pair<long long, long long> p[n];
for(int i=0; i<n; i++){
cin >> p[i].f >> p[i].s;
}
sort(p, p+n);
long long pr[n+1], m[n];pr[0]=0;
for(int i=0; i<n; i++){
pr[i+1]=pr[i]+p[i].s;
}
m[n-1]=pr[n]-p[n-1].f;
for(int i=n-2; i>=0; i--){
m[i]=max(m[i+1], pr[i+1]-p[i].f);
}
long long ans=0;
for(int i=0; i<n; i++){
ans=max(ans, m[i]-pr[i]+p[i].f);
}
cout << ans;
}
int main(){
cin.tie(nullptr)->sync_with_stdio(0);
int t=1;
//cin >> t;
while(t--){
solve();
cout << "\n";
}
return 0;
}
