from math import gcd


N = int(input())
xys = [tuple(map(int, input().split())) for _ in range(N)]

ret = 0
memo: dict[tuple[int, int, int, int], int] = {}

for i in range(N):
    for j in range(i + 1, N):
        x1, y1 = xys[i]
        x2, y2 = xys[j]
        cx = x1 + x2
        cy = y1 + y2

        dx = x2 - x1
        dy = y2 - y1
        g = gcd(dx, dy)
        dx //= g
        dy //= g

        if (cx, cy, dy, -dx) in memo:
            ret += memo[(cx, cy, dy, -dx)]

        memo[(cx, cy, dx, dy)] = memo.get((cx, cy, dx, dy), 0) + 1
        memo[(cx, cy, -dx, -dy)] = memo.get((cx, cy, -dx, -dy), 0) + 1

print(ret)