116A.cpp

//116A
#include<iostream>
using namespace std;
int main(){
	int n;
	int a,b;
	int cap=0;
	cin>>n;
	int x=0;
	for(int i=0;i<n;i++){
		cin>>a>>b;
		x=x-a;
		x=x+b;
		if(x>cap) cap=x;
	}
	cout<<cap;
	return 0;
}