【题解】【上海】【评测队列】

#include <iostream>
using namespace std;

int a[200005], b[200005], n;
long long ans, t;
int main() {
	cin >> n;

	for (int i = 1; i <= n; i++)
		cin >> a[i] >> b[i];

	ans = t = 0;

	for (int i = 1; i <= n; i++) {
		t += a[i];
		ans = max(ans, t);
		ans += b[i];
	}

	cout << ans;
	return 0;
}