N = int(input())**2

if(N <= 4):
    print(-1)
    exit()

edge = set()
for i in range(N):
    for di in [-4,-2,2,4]:
        new = (i + di) % N
        a,b = min(i,new), max(i,new)
        edge.add((a+1,b+1))

def check(N,edge_list):
    edge = [[] for _ in range(N+1)]
    for a,b in edge_list:
        edge[a].append(b)
        edge[b].append(a)
    
    for i in range(1,N+1):
        if(sum(edge[i]) % N != 4*i % N):return False
    return True

if(not check(N,edge)):
    print(-1)
else:
    print(len(edge))
    for i in edge:
        print(*i)