#include <bits/stdc++.h>
#define rep(i,n) for(int i = 0; i < (int)(n); i++)
#define repr(i,n) for(int i = (int)(n-1); i >= 0; i--)
#define rep2(i,x,n) for(int i = (int)(x); i < (int)(n); i++)
#define repit(itr,x) for(auto itr = x.begin(); itr != x.end(); itr++)
#define repitr(ritr,x) for(auto ritr = x.rbegin(); ritr != x.rend(); ritr++)
#define ALL(n) begin(n), end(n)
using ll = long long;
using namespace std;

int main(){
	int n;
	cin >> n;
	vector<int> a(n*2);
	rep(snip_i, n*2) cin >> a.at(snip_i);
	
	ll ans = 0;
	ll p1 = 0, p2 = 0;
	rep(i, n+1){
		if(i == 0){
			rep(j, n){
				p2 += a.at(j*2); p1 += a.at(j*2+1);
			}
		}else{
			int ii = i - 1;
			p1 += a.at(ii*2); p1 -= a.at(ii*2+1);
			p2 -= a.at(ii*2); p2 += a.at(ii*2+1);
		}
		ll dif = p1 - p2;
		if(i == 0 || ans < dif) ans = dif;
	}
	cout << ans << endl;
	return 0;
}