#include <algorithm>
#include <iostream>
using namespace std;
const int N = 500000;
const long long INF = 0x3f3f3f3f3f3f3f3fLL;
long long aa[N];
int bb[N], ii[N];
int main() {
ios_base::sync_with_stdio(false), cin.tie(NULL);
int n; cin >> n;
for (int i = 0; i < n; i++)
cin >> aa[i] >> bb[i], ii[i] = i;
sort(ii, ii + n, [] (int i, int j) { return aa[i] < aa[j]; });
long long ans = 0, s = 0, t = -INF;
for (int h = 0; h < n; h++) {
int i = ii[h], b = bb[i];
long long a = aa[i];
t = max(t, a - s), s += b;
ans = max(ans, s - a + t);
}
cout << ans << '\n';
return 0;
}
