#include <bits/stdc++.h>
using namespace std;
#ifdef LOCAL
#define deb(...) logger(#__VA_ARGS__, __VA_ARGS__)
template<typename ...Args>
void logger(string vars, Args&&... values) {
cerr<<vars<<" = ";
string delim="";
(...,(cerr<<delim<<values,delim=", "));
cerr<<"\n";
}
#else
#define deb(...) logger(#__VA_ARGS__, __VA_ARGS__)
template<typename ...Args>
void logger(string vars, Args&&... values) {}
#endif
#define pb push_back
#define sz(x) (int)(x.size())
typedef long long ll;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;
template<typename T> inline void maxa(T& a,T b){a=max(a,b);}
template<typename T> inline void mina(T& a,T b){a=min(a,b);}
int main(){
cin.sync_with_stdio(0);
cin.tie(0); cout.tie(0);
#ifdef LOCAL
freopen("input.txt","r",stdin);
freopen("output.txt","w",stdout);
#endif
int n; cin>>n;
vector<pll> art;
ll sum=0;
for(int i=0;i<n;i++){
ll a,b; cin>>a>>b;
sum+=b;
art.pb({a,b});
}
sort(art.begin(),art.end());
vector<ll> psa(n+1),pref(n+1);
for(int i=1;i<=n;i++){
psa[i]=art[i-1].second+psa[i-1];
}
pref[0]=-art[0].first;
for(int i=1;i<n;i++){
pref[i]=min(psa[i]-art[i].first,pref[i-1]);
}
ll ans=0;
for(int i=n;i>=1;i--){
maxa(ans,psa[i]-art[i-1].first-pref[i-1]);
}
cout<<ans<<"\n";
}
