#include <bits/stdc++.h>
#include <fstream>
#define endl '\n'
#define mod 998244353
#define INF 100000000
//#define ll long long
///#define cin fin
///#define cout fout
#define fi first
#define se second
using namespace std;
///ofstream fout("herding.out");
///ifstream fin("herding.in");
int main()
{
ios_base::sync_with_stdio(0);cout.tie(0);cin.tie(0);
long long n, ans = 0; cin >> n; pair<long long ,long long> arr[n]; long long dp[n+1]= {};
for(int i = 0; i < n; i++) {
cin >> arr[i].first >> arr[i].second;
}
sort(arr,arr+n);
for(int i = 1; i <= n; i++) {
dp[i] = max(dp[i-1],arr[i-1].first) + arr[i-1].second;
ans = max(ans,dp[i]-arr[i-1].first);
}
cout << ans;
return 0;
}
