def main():
    N = int(input())
    XY = []
    for i in range(N):
        x, y = map(int, input().split())
        XY.append((x, y))

    d_list = []
    for i in range(N):
        for j in range(i+1, N):
            dsq = (XY[i][0]-XY[j][0])**2 + (XY[i][1]-XY[j][1])**2
            d_list.append((dsq, i, j))

    d_list.sort()
        
    #print(d_list)
    
    ans = 0
    popped = [0]*N
    for d, a, b in d_list:
        if a == 0 and popped[b] == 0:
            ans += 1
            popped[b] = 1
        elif popped[a] == 0 and popped[b] == 0:
            popped[a] = 1
            popped[b] = 1
    print(ans)
    #print(popped)    
    
main()