#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define f first
#define s second
#define pb push_back
#define ep emplace
#define eb emplace_back
#define lb lower_bound
#define ub upper_bound
#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()
#define uniquev(v) sort(all(v)), (v).resize(unique(all(v)) - (v).begin())
#define mem(f,x) memset(f , x , sizeof(f))
#define sz(x) (int)(x).size()
#define __lcm(a, b) (1ll * ((a) / __gcd((a), (b))) * (b))
#define mxx *max_element
#define mnn *min_element
#define cntbit(x) __builtin_popcountll(x)
#define len(x) (int)(x.length())
const int N = 1e6 + 100;
ll solve() {
int n;
cin >> n;
vector <pair <ll, ll>> st;
for (int i = 0; i < n; i++) {
ll a, b;
cin >> a >> b;
st.pb({a, b});
}
sort(all(st));
ll ans = 0, mi = 0, s = 0;
for (int i = 0; i < n; i++) {
mi = min(mi, s - st[i].f);
ans = max(ans, s - st[i].f - mi + st[i].s);
s += st[i].s;
}
return ans;
}
// s[i] - mx - (s[j] - mi)
int main() {
int t = 1;
while (t--) {
cout << solve() << '\n';
}
}
