#include <bits/stdc++.h>
#define startt ios_base::sync_with_stdio(false);cin.tie(0);
typedef long long ll;
using namespace std;
#define vint vector<int>
#define all(v) v.begin(), v.end()
#define MOD 1000000007
#define MOD2 998244353
#define MX 1000000000
#define MXL 1000000000000000000
#define PI (ld)2*acos(0.0)
#define nax 200005
#define pb push_back
#define sc second
#define fr first
#define int long long
//#define endl '\n'
#define ld long double
#define NO cout << "NO" << endl
#define YES cout << "YES" << endl
void solve()
{
int n;
cin >> n;
vector<pair<int, int>> a(n);
for(int i = 0; i < n; i++)
{
cin >> a[i].fr >> a[i].sc;
}
sort(all(a));
int sum = a[0].sc;
int ans = a[0].sc;
for(int i = 1; i < n; i++)
{
sum = max(a[i].sc, sum-(a[i].fr-a[i-1].fr)+a[i].sc);
ans = max(ans, sum);
}
cout << ans << endl;
}
int32_t main(){
startt
int t = 1;
//cin >> t;
while (t--) {
solve();
}
}
