n=int(input()) coord=[] for i in range(n): x,y=map(int,input().split()) coord.append((x,y,i)) dist=[] for i in range(n): tmp=[] for j in range(n): if i==j: continue d=(coord[i][0]-coord[j][0])**2+(coord[i][1]-coord[j][1])**2 tmp.append((d, j)) tmp=sorted(tmp) dist.append(tmp) cnt=0 removed=set([]) for i in range(1,n): for j in range(n-1): x=dist[i][j][1] if i in removed: break elif x in removed: continue elif x==0: removed.add(i) cnt+=1 else: removed.add(x) removed.add(i) break print(cnt)