#include <iostream>
#include <cstdio>
#include <climits>
using namespace std;

int main() {
	int n, a, b, sum, max;
	sum=0;
	max=INT_MIN;
	scanf("%d", &n);
	while(n--) {
		scanf("%d%d", &a, &b);
		sum=sum-a+b;
		if(sum>max) max=sum;
	}
	printf("%d", max);
	return 0;
}