#include <bits/stdc++.h>

int ri() {
	int n;
	scanf("%d", &n);
	return n;
}
int main() {
	int n = ri();
	int a[n];
	for (auto &i : a) {
		int x = ri();
		int y = ri();
		i = x - y;
	}
	int64_t sum[n + 1], backsum[n + 1];
	sum[0] = 0;
	backsum[n] = 0;
	for (int i = 0; i < n; i++) sum[i + 1] = sum[i] + a[i];
	for (int i = n; i--; ) backsum[i] = backsum[i + 1] - a[i];
	int64_t res = 0;
	for (int i = 0; i <= n; i++) res = std::max(res, sum[i] + backsum[i]);
	printf("%" PRId64 "\n", res);
	return 0;
}