#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<ll, ll> pii;
#define pb push_back
#define F first
#define S second
//#define int long long
const int maxn = 1e6 + 10;
const int LOG = 21;
const int mod = 1e9 + 7;
ll n, b[maxn], ans;
int main() {
cin >> n;
vector<pii> a(n);
for (int i = 0; i < n; i++) {
cin >> a[i].F >> a[i].S;
}
sort(a.begin(), a.end());
b[0] = a[0].S;
ans = b[0];
for (int i = 1; i < n; i++) {
b[i] = max(a[i].S, b[i - 1] + a[i].S - (a[i].F - a[i - 1].F));
ans = max(ans, b[i]);
}
cout << ans << endl;
}
