#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include <utility>
#include <tuple>
#include <queue>
#include <deque>
#include <map>
#include <set>
#include <cmath>
#include <iomanip>
#define rep(i, n) for(int i = 0; i < (int)(n); ++i)
using namespace std;

int main(void) {
    int N;
    cin >> N;
    vector<int> A(N);
    rep(i, N) {
        int a, b;
        cin >> a >> b;
        A[i] = a - b;
    }
    vector<long long> sum(N + 1, 0);
    rep(i, N) sum[i + 1] = sum[i] + A[i];
    long long ans = -1e18;
    rep(i, N + 1) ans = max(ans, sum[i] - (sum[N] - sum[i]));
    cout << ans << endl;
    return 0;
}