#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef vector<int> vi;
typedef pair<int,int> pi;
#define REP(i,a,b) for(int i=a;i<b;i++)
#define F first
#define S second
#define PB push_back
#define MP make_pair
const int m=1e9+7;
int main(){
//ios::sync_with_stdio(0);
// cin.tie(0);
//freopen("test_input.txt", "r", stdin);
//freopen("test_output.txt", "w", stdout);
#define int long long
int n;cin>>n;
vector<pair<ll,ll>> arr(n);
REP(i,0,n)cin>>arr[i].F>>arr[i].S;
sort(arr.begin(),arr.end());
int ans=0;int a=0;
REP(i,0,n){
a=arr[i].S;
ans=max(ans,a);
a+=arr[i].F;
REP(j,i+1,n){
a+=arr[j].S;
ans=max(ans,a-arr[j].F);
}
// cout<<i<<" "<<ans<<" l";
}
cout<<ans;
return 0;
}
