from collections import defaultdict
N=int(input())
data=[]
for _ in range(N):
    x,y=map(int, input().split())
    data.append((x,y))
d=defaultdict(list)
for i in range(N):
    for j in range(i+1,N):
        x0,y0=data[i]
        x1,y1=data[j]
        d[(x0-x1)**2+(y0-y1)**2].append((i,j))

used=set()
cnt=0
for t in sorted(list(d.keys())):
    for i,j in d[t]:
        if i==0 and j not in used:
            used.add(j)
            cnt+=1
        if i not in used and j not in used:
            used.add(i)
            used.add(j)
print(cnt)