#include <bits/stdc++.h>
using namespace std::literals::string_literals;
using i64 = std::int_fast64_t;
using std::cout;
using std::cerr;
using std::endl;
using std::cin;

template<typename T>
std::vector<T> make_v(size_t a){return std::vector<T>(a);}

template<typename T,typename... Ts>
auto make_v(size_t a,Ts... ts){
  return std::vector<decltype(make_v<T>(ts...))>(a,make_v<T>(ts...));
}

int main() {
	int n; scanf("%d", &n); std::vector<int> a(2 * n);
	for(int i = 0; i < 2 * n; i++) scanf("%d", &a[i]);

	i64 now = 0, sum = 0;
	for(int i = 0; i < n; i++) now += a[2 * i + 1];
	for(auto v: a) sum += v;

	i64 ans = now - (sum - now);
	for(int i = 0; i < n; i++) {
		now += a[2 * i];
		now -= a[2 * i + 1];
		
		ans = std::max(ans, now - (sum - now));
	}
	printf("%ld\n", ans);
	return 0;
}