#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define pb push_back
#define fi first
#define se second
constexpr ll MAXN=5e5+5,MAXV=1e5,MOD=1e9+7,INF=1e18;
ll n,m,i,j,p,k,ans,dem,st,en;
struct h{
ll a,b;
} a[MAXN];
bool cmp(h a,h b){
return a.a<b.a;
}
int main(){
ios::sync_with_stdio(0);
cin.tie(0);cout.tie(0);
// freopen("test.inp","r",stdin);
// freopen("test.out","w",stdout);
cin>>n;
for(i=1;i<=n;i++){
cin>>a[i].a>>a[i].b;
}
sort(a+1,a+n+1,cmp);
for(i=1;i<=n;i++)
a[i].b+=a[i-1].b;
ll mi=-INF;
for(i=1;i<=n;i++){
mi=max(mi,-a[i-1].b+a[i].a);
ans=max(ans,a[i].b-a[i].a+mi);
}
cout<<ans;
}
