import sys
import itertools

input=sys.stdin.readline


def main(args):
    n = int(input())
    
    balloons = []
    for _ in range(n):
        x, y = map(int,input().split())
        balloons.append((x, y))
    
    dist = []
    for i in range(n):
        for j in range(i+1,n):
            x1, y1 = balloons[i]
            x2, y2 = balloons[j]
            d = (x2-x1)**2+(y2-y1)**2
            dist.append((d, i, j))
        
    dist.sort()
    
    removed = [0]*n
    ans = 0
    for d in dist:
        a = d[1]
        b = d[2]
        if a == 0:
            if removed[b] == 0:
                ans += 1
                removed[b] = 1
        else:
            if removed[a] == 0 and removed[b] == 0:
                removed[a] = 1
                removed[b] = 1
    
    print(ans)
    
if __name__ == '__main__':
    main(sys.argv[1:])