“Codeforces 233 A Solution Python” Ответ

Codeforces 233 A Solution Python

n=int(input())
m=n+1
if n%2!=0 :
    print("-1")
else :
    for i in range (1,m) :
        if i%2==0 :
            print(i-1)
        else :
            print(i+1)