#include <bits/stdc++.h>
using namespace std;
#define endl '\n'
#define ll long long
#define int long long
#define ull unsigned long long
#define lb lower_bound
#define ub upper_bound
void solve() {
int n;
cin >> n;
vector<pair<int, int>> vt = {{0, 0}};
for (int i = 1; i <= n; i++){
int a, b;
cin >> a >> b;
vt.push_back({a, b});
}
sort(vt.begin(), vt.end());
int dp[n + 5];
memset(dp, 0, sizeof(dp));
dp[1] = vt[1].second;
for (int i = 2; i <= n; i++){
dp[i] = max({dp[i - 1] + vt[i].second - (vt[i].first - vt[i - 1].first), vt[i].second});
}
int x = 0;
for (int i = 1; i <= n; i++)x = max(x, dp[i]);
cout << x << endl;
}
signed main() {
ios::sync_with_stdio(false);
cin.tie(0);
cout.tie(0);
int t = 1;
//cin >> t;
while (t--) {
solve();
}
}
