#include <iostream>
#include <fstream>
#include <iomanip>
#include <vector>
#include <set>
#include <map>
#include <cstring>
#include <string>
#include <cmath>
#include <cassert>
#include <ctime>
#include <algorithm>
#include <sstream>
#include <list>
#include <queue>
#include <deque>
#include <stack>
#include <cstdlib>
#include <cstdio>
#include <iterator>
#include <functional>
#include <unordered_set>
#include <unordered_map>
#include <stdio.h>
#include <bitset>
#include <cstdint>
#include <cassert>
#include <functional>
#include <complex>
#include <climits>
#include <random>
using namespace std;
#define ll long long
#define pb push_back
#define ull unsigned long long
#define F first
#define S second
#define all(v) v.begin(), v.end()
int n;
pair<ll, ll> ab[500005];
ll dp[500005];
void solve(){
cin >> n;
for(int i = 1; i <= n; i++){
cin >> ab[i].F >> ab[i].S;
}
sort(ab + 1, ab + 1 + n);
dp[1] = ab[1].F + ab[1].S;
ll mx = 0LL;
for(int i = 2; i <= n; i++){
dp[i] = max(dp[i - 1] + ab[i].S, ab[i].F + ab[i].S);
mx = max(mx, dp[i] - ab[i].F);
}
cout << mx;
}
signed main(){
ios_base::sync_with_stdio(false);
cin.tie(NULL), cout.tie(NULL);
int xach = 1;
//cin >> xach;
while(xach--) solve();
}
/*
*
*/
