#include <iomanip>
#include <iostream>
#include <functional>
#include <algorithm>
#include <math.h>
#include <cmath>
#include <string>

using namespace std;

int main(){
	int n;
	int s = 0, z, x, v = 0;
	cin >> n;
	for (int i = 0; i < n; i++){
		cin >> x >> z;
		s = s + z - x;
		if (s >v){
			v = s;
		}
	}
	cout << v;
}