mod = 1000000007
eps = 10**-9


def main():
    import sys
    from math import hypot
    input = sys.stdin.readline

    N = int(input())
    X = []
    Y = []
    for _ in range(N):
        x, y = map(int, input().split())
        X.append(x)
        Y.append(y)

    ev = []
    for i in range(N):
        xi, yi = X[i], Y[i]
        for j in range(i+1, N):
            xj, yj = X[j], Y[j]
            ev.append(((xi-xj)**2 + (yi-yj) ** 2, i, j))
    ev.sort(key=lambda x: x[0])
    seen = [0] * N
    ans = 0
    for _, i, j in ev:
        if i == 0:
            if not seen[j]:
                ans += 1
                seen[j] = 1
        else:
            if seen[i] == seen[j] == 0:
                seen[i] = 1
                seen[j] = 1
    print(ans)


if __name__ == '__main__':
    main()