#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
#define fi first
#define se second
#define pii pair<int,int>
#define pll pair<long long,long long>
#define pb push_back
#define debug(x) cerr<<#x<<"="<<x<<endl
#define pq priority_queue
#define inf 1e18;
#define rep(i,a,b) for (ll i=a;i<(b);i++)
#define MP make_pair
#define SZ(x) (int(x.size()))
#define mod 1000000007
#define ALL(x) x.begin(),x.end()
#define endl "\n"
void inc(ll &a,ll b) {a=(a+b)%mod;}
void dec(ll &a,ll b) {a=(a-b+mod)%mod;}
int lowbit(ll x) {return x&(-x);}
int main(){
ios::sync_with_stdio(0);
cin.tie(0);
ll n;cin>>n;
vector<pll>alist;
rep(i,0,n){
ll a,b;cin>>a>>b;
alist.pb(MP(a,b));
}
sort(ALL(alist));
ll ans=0,sum=0,mn=inf;
rep(i,0,n){
mn=min(mn,sum-alist[i].fi);
sum+=alist[i].se;
ans=max(ans,sum-alist[i].fi-mn);
}
cout<<ans<<endl;
return 0;
}
