from math import gcd

n = int(input())
X = [0] * n
Y = [0] * n
for i in range(n):
    X[i], Y[i] = map(int, input().split())
    X[i] *= 2
    Y[i] *= 2

ans = 0
add = {}
for i in range(n):
    for j in range(i + 1, n):
        cx = (X[i] + X[j]) // 2
        cy = (Y[i] + Y[j]) // 2
        c = (cx << 31) + cy

        dx = X[i] - X[j]
        dy = Y[i] - Y[j]
        g = gcd(dx, dy)
        dx //= g
        dy //= g
        if dx < 0:
            dx = -dx
            dy = -dy
        if dx == 0:
            dy = 1
        d = (dx << 31) + dy
        ans += add.get((c, d), 0)

        dx, dy = dy, -dx
        if dx < 0:
            dx = -dx
            dy = -dy
        if dx == 0:
            dy = 1

        d = (dx << 31) + dy
        add[(c, d)] = add.get((c, d), 0) + 1


print(ans)