#include <bits/stdc++.h>
using namespace std;
#ifdef LOCAL
#include "debug.h"
#else
#define dbg(...) 42
#endif
struct SegmentTree {
};
int main() {
ios::sync_with_stdio(false);
cin.tie(nullptr);
int n;
cin >> n;
vector<array<int64_t, 2>> v(n);
for (int i = 0; i < n; i++) {
cin >> v[i][0] >> v[i][1];
}
sort(v.begin(), v.end());
vector<int64_t> a(n), b(n);
for (int i = 0; i < n; i++) {
a[i] = v[i][0];
b[i] = v[i][1];
}
int64_t res = 0, sum = 0, mx = 0;
for (int i = 0; i < n; i++) {
sum += b[i];
mx = min(mx, sum - a[i] - b[i]);
res = max(res, sum - mx - a[i]);
}
cout << res << '\n';
return 0;
}
