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):
            d = (XY[i][0]-XY[j][0])**2 + (XY[i][1]-XY[j][1])**2
            d_list.append((d, i, j))

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