#include <bits/stdc++.h>
#define ff first
#define ss second
#define endl '\n'
using namespace std;
const long long INF = (long long) 1e18;
const int mod = (int) 1e9+7;
const int MAXN = (int) 5e5+5;
typedef long long ll;
typedef unsigned long long ull;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;
ll n;
ll pre[MAXN];
struct p{
ll v, s;
bool operator < (p other) const{
if(s == other.s){
return v < other.v;
}
return s < other.s;
};
} ps[MAXN];
int main(){
ios_base::sync_with_stdio(false);
cin.tie(nullptr);cout.tie(nullptr);
#ifdef Local
freopen("C:/Users/Admin/Desktop/Yazilim/C/IO/int.txt","r",stdin);
freopen("C:/Users/Admin/Desktop/Yazilim/C/IO/out.txt","w",stdout);
#endif
cin>>n;
for(int i = 0; i < n; i++){
cin>>ps[i].s>>ps[i].v;
}
sort(ps, ps + n);
pre[0] = ps[0].v;
for(int i = 1; i < n; i++){
pre[i] = pre[i - 1] + ps[i].v;
}
ll ans = ps[0].v,
mx = ps[0].s;
for(int i = 1; i < n; i++){
ans = max(ans, pre[i] - ps[i].s + mx);
ans = max(ans, ps[i].v);
mx = max(mx, -pre[i - 1] + ps[i].s);
}
cout<<ans<<endl;
#ifdef Local
cout<<endl<<fixed<<setprecision(2)<<1000.0 * clock() / CLOCKS_PER_SEC<< " milliseconds ";
#endif
}
