class Star:
    def __init__(self):
        self.x = None
        self.y = None

    def dist_sqr(self, star):
        return (self.x - star.x) ** 2 + (self.y - star.y) ** 2

def find_constellations(M, S):
    for i in range(len(S)):
        for j in range(i+1, len(S)):
            M[i][j] = Star.dist_sqr(S[i], S[j])
            M[j][i] = M[i][j]
    c = 0
    for i in range(len(S)):
        D = {}
        for j in range(len(S)):
            if i == j:
                continue
            if M[i][j] not in D:
                D[M[i][j]] = 1
            else:
                D[M[i][j]] += 1
        for k in D:
            if D[k] >= 2:
                c += int(D[k] * (D[k] - 1) / 2)
    return c

if __name__ == "__main__":
    n = int(input())
    M = [[None] * n] * n
    S = []
    for i in range(n):
        st = input().split()
        star = Star()
        star.x = int(st[0])
        star.y = int(st[1])
        S.append(star)
    print(find_constellations(M, S))