from math import gcd

N = int(input())
X, Y = [0] * N, [0] * N
for i in range(N):
    X[i], Y[i] = map(int, input().split())
kumi = []
for i in range(N):
    for j in range(i + 1, N):
        kumi.append(((X[i] - X[j]) ** 2 + (Y[i] - Y[j]) ** 2, i, j))
kumi.sort()
used = set()
tilt = set()
ans = []
for d, x, y in kumi:
    w, h = X[x] - X[y], Y[x] - Y[y]
    if w == 0:
        katamuki = 10000
    else:
        katamuki = h / w
    if x not in used and y not in used and katamuki not in tilt:
        ans.append((x + 1, y + 1))
        used.add(x)
        used.add(y)
        tilt.add(katamuki)
print(len(ans))
for x, y in ans:
    print(x, y)