#include <iostream>
#include <vector>
#include <string>
#include <algorithm>
#include <cstdio>
#include <cstring>
#include <cmath>
using namespace std;
using ll = long long;

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);

    int n;
    cin >> n;

    ll s = 0;
    vector<int> a(n);
    for (int i = 0; i < n; i++) {
        int x, y;
        cin >> x >> y;
        s += a[i] = y - x;
    }

    ll r = s;
    for (int i = 0; i < n; i++) {
        s -= a[i] * 2;
        r = max(r, s);
    }

    cout << r << endl;

    return 0;
}