#include <bits/stdc++.h>

using namespace std;
typedef long long ll;

#define INF (long long)(10e9+7)
#define REP(i,n) for(ll i = 0; i < n; i++)
#define REP1(i,n) for(ll i = 1; i <= n; i++)
ll A[200100], suml[100100], sumr[100100];
int main(void)
{
    ll N;
    cin >> N;
    REP(i, 2*N) cin >> A[i];
    suml[0] = 0;
    sumr[0] = 0;
    REP(i, N) {
        suml[i+1] = suml[i] + A[i*2] - A[i*2+1];
        sumr[i+1] = sumr[i] + A[(N-i)*2-1] - A[(N-i)*2-2];
    }
    ll m = -INF;
    for(ll i = 0; i <= N; i++) {
        m = max(m, suml[i] + sumr[N-i]);
    }
    cout << m << endl;


    
}