#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<ll,ll> pll;
typedef long double ld;
const ll MOD=1e9+7;
const ll N=5e5+5;
const ld pi=3.14159265359;
const ll INF=(1LL<<62);
#define REP(i,n) for(ll i=0;i<n;i++)
#define REP1(i,n) for(ll i=1;i<=n;i++)
#define pb push_back
#define mp make_pair
#define X first
#define Y second
#define setp setprecision
#define lwb lower_bound
#define SZ(a) (ll)a.size()
ll n,x,y,dp[N],ans;
vector<pll> v;
int main(){
ios_base::sync_with_stdio(0);cin.tie(0);
cin>>n;
REP(i,n){
cin>>x>>y;v.pb(mp(x,y));
}
sort(v.begin(),v.end());
REP(i,n)v[i].Y-=(v[i+1].X-v[i].X);
REP(i,n){
dp[i]=max(v[i].Y,v[i].Y+(i?dp[i-1]:0));
ans=max(ans,dp[i]+v[i+1].X-v[i].X);
}
cout<<ans<<"\n";
return 0;
}
