#include <bits/stdc++.h>
using namespace std;

int main() {
    int n;
    cin >> n;
    vector<int64_t> s(n + 1);
    for (int i = 0; i < n; i++) {
        int64_t x, y;
        cin >> x >> y;
        s.at(i + 1) = s.at(i) + x - y;
    }
    cout << 2 * *max_element(s.begin(), s.end()) - s.at(0) - s.at(n) << endl;
}