import itertools

n = int(input())
C = []
for i in range(n):
    x, y = map(int,input().split())
    C.append((x, y, i))

dist = []
for U, V in itertools.combinations(C, 2):
    ux, uy, ui = U
    vx, vy, vi = V
    dist.append(((ux-vx)**2+(uy-vy)**2, min(ui,vi), max(ui,vi)))
    
dist.sort()
broken = [0]*n
ans = 0
for dd in dist:
    d, ui, vi = dd
    if ui == 0:
        if broken[vi] == 0:
            ans += 1
            broken[vi] = 1
    else:
        if broken[ui] != broken[vi]:
            continue
        else:
            broken[ui] = 1
            broken[vi] = 1
            
print(ans)