from sys import stdin
def main():
    #入力
    readline=stdin.readline
    N=int(readline())
    A=list(map(int,readline().split()))

    S_l_1=[0]*N
    S_l_2=[0]*N
    S_r_1=[0]*N
    S_r_2=[0]*N

    for i in range(N):
        if i==0:
            S_l_1[i]=A[2*i]
            S_l_2[i]=A[2*i+1]
        else:
            S_l_1[i]=S_l_1[i-1]+A[2*i]
            S_l_2[i]=S_l_2[i-1]+A[2*i+1]
    S_l_1.insert(0,0)
    S_l_2.insert(0,0)

    for i in range(N-1,-1,-1):
        if i==N-1:
            S_r_1[i]=A[2*i+1]
            S_r_2[i]=A[2*i]
        else:
            S_r_1[i]=S_r_1[i+1]+A[2*i+1]
            S_r_2[i]=S_r_2[i+1]+A[2*i]
    S_r_1.append(0)
    S_r_2.append(0)

    score_h=0
    score_t=0
    res=0
    for k in range(N+1):
        score_h=S_l_1[k]+S_r_1[k]
        score_t=S_l_2[k]+S_r_2[k]
        res=max(res,score_h-score_t)

    print(res)

if __name__=="__main__":
    main()