/// @author : Hoang Manh Linh
#include <bits/stdc++.h>
using namespace std;
const int MAXN = 5e5 + 5;
using i64 = long long;
using pll = pair<i64, i64>;
int n;
pll a[MAXN];
i64 dp[MAXN];
int main(int argc, char **argv) {
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
cin >> n;
for(int i = 1; i <= n; i++)
cin >> a[i].first >> a[i].second;
sort(a + 1, a + n + 1);
for(int i = 1; i <= n; i++)
dp[i] = max(dp[i - 1] + a[i].second - (a[i].first - a[i - 1].first), a[i].second);
i64 ans = *max_element(dp + 1, dp + n + 1);
cout << ans;
}
