n=int(input())
m=list(range(1,n+1))
even=[]
odd=[]
for x in range (0,len(m)):
    if m[x]%2==0:
        even.append(m[x])
    else: odd.append(m[x])
 
output = [[a, b] for a in even
          for b in odd ]
print(output)