#include<stdio.h>
int main()
{
	long long int n;
	scanf("%lld", &n);
	long long int i;
	long long int a[200005];
	for (i = 0; i < 2 * n; i++)
		scanf("%lld", &a[i]);
	long long int l[100005], r[100005];
	l[0] = 0;
	for (i = 0; i < n; i++)
		l[i + 1] = l[i] + a[2 * i] - a[2 * i + 1];
	r[n] = 0;
	for (i = n - 1; i >= 0; i--)
		r[i] = r[i + 1] + a[2 * i + 1] - a[2 * i];
	long long int ans = l[n] + r[n];
	for (i = 0; i < n; i++)
		if (ans < l[i] + r[i])
			ans = l[i] + r[i];
	printf("%lld\n", ans);
	return 0;
}