import java.util.*;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int[] arr = new int[n + 2];
        long[] left = new long[n + 2];
        for (int i = 1; i <= n; i++) {
            arr[i] = sc.nextInt() - sc.nextInt();
            left[i] = left[i - 1] + arr[i];
        }
        long[] right = new long[n + 2];
        for (int i = n; i >= 1; i--) {
            right[i] = right[i + 1] - arr[i];
        }
        long max = Long.MIN_VALUE;
        for (int i = 0; i <= n; i++) {
            max = Math.max(max, left[i] + right[i + 1]);
        }
        System.out.println(max);
    }
}