import sys, math
from heapq import heappop, heappush
input = sys.stdin.readline

def isqrt(n):
	rn = math.sqrt(n)
	ok = max(0, int(rn - 2))
	ng = int(rn + 2)
	while(ng - ok > 1):
		k = (ok + ng) >> 1
		if(k * k <= n):
			ok = k
		else:
			ng = k
	return ok


"""
Main Code
"""

n = int(input())
planet = [list(map(int, input().split())) for _ in [0] * n]

route = [[] for _ in [0] * n]
for i in range(0, n-1):
	for j in range(i+1, n):
		p1 = planet[i]
		p2 = planet[j]
		d = (p1[0] - p2[0]) ** 2 + (p1[1] - p2[1]) ** 2
		if(p1[2] != p2[2]):
			r1 = p1[0] ** 2 + p1[1] ** 2
			r2 = p2[0] ** 2 + p2[1] ** 2
			d = r1 + r2 - isqrt(4 * r1 * r2)
		route[i].append((j, d))
		route[j].append((i, d))

def check(mid):
	stk = [0]
	visited = [False] * n
	while(stk):
		v = stk.pop()
		if(v == n - 1):
			return True
		for nv, nd in route[v]:
			if(visited[nv] or nd > mid):
				continue
			visited[nv] = True
			stk.append(nv)
	return False

ok = 10 ** 10
ng = -1
while(ok - ng > 1):
	mid = (ok + ng) >> 1
	if(check(mid)):
		ok = mid
	else:
		ng = mid

ans = ok
print(ans)