#include<bits/stdc++.h>
using namespace std;
const int N = 500010;
#define ll long long int
#define F first
#define S second
pair<ll,ll> v[N];
ll dp[N][2];
int n;
ll f(int x,int y) {
if(dp[x][y]>=0) return dp[x][y];
ll aux = v[x].S-v[x].F+v[x-1].F;
if(y) {
if(x==n) return aux;
return dp[x][y]=max(aux,aux+f(x+1,y));
} else {
if(x==n) return v[x].S;
return dp[x][y]=max({v[x].S,f(x+1,y),v[x].S+f(x+1,y+1)});
}
}
int main() {
ios::sync_with_stdio(false);
cin.tie(0);
cin>>n;
for(int i=1;i<=n;i++) {
cin>>v[i].F>>v[i].S;
}
sort(v+1,v+n+1);
memset(dp,-1,sizeof(dp));
cout<<f(1,0)<<"\n";
}
