#include "bits/stdc++.h"
using namespace std;
typedef long long ll;

int main() {
    int n; cin >> n;
    ll ans = 0;
    vector<ll> v(n), a(n + 1, 0), b(n + 1, 0);
    for (int i = 0; i < n; i++) {
        int x, y; cin >> x >> y;
        v[i] = x - y;
    }
    for (int i = 0; i < n; i++) {
        a[i + 1] = v[i] + a[i];
        b[n - i - 1] = -v[n - i - 1] + b[n - i];
    }
    for (int i = 0; i <= n; i++) {
        ans = max(ans, a[i] + b[i]);
    }
    cout << ans << endl;
    return 0;
}