/**
S - (a_max - a_min) = pre_b(j) - a(j) - (pre_b(i - 1) - a(i))
**/
#include <bits/stdc++.h>
using namespace std;
int n;
struct Data {
long long size, value;
bool operator < (const Data &other) const {
return (size < other.size);
}
};
#define MAX_N 500500
Data d[MAX_N];
int main() {
ios_base::sync_with_stdio(false);cin.tie(nullptr);
cin >> n;
for (int i = 1; i <= n; ++i) cin >> d[i].size >> d[i].value;
sort(d + 1, d + 1 + n);
for (int i = 1; i <= n; ++i) d[i].value += d[i - 1].value;
long long ans = 0, pref = d[1].size;
for (int i = 1; i <= n; ++i) {
ans = max(ans, d[i].value - d[i].size - pref);
pref = min(pref, d[i - 1].value - d[i].size);
}
cout << ans;
return 0;
}
