import math
from collections import defaultdict

class UnionFind:
    def __init__(self, size):
        self.parent = list(range(size))
        self.rank = [0] * size

    def find(self, x):
        if self.parent[x] != x:
            self.parent[x] = self.find(self.parent[x])
        return self.parent[x]

    def unite(self, x, y):
        x = self.find(x)
        y = self.find(y)
        if x == y:
            return
        if self.rank[x] < self.rank[y]:
            self.parent[x] = y
        else:
            self.parent[y] = x
            if self.rank[x] == self.rank[y]:
                self.rank[x] += 1

def main():
    N = int(input())
    points = []
    for _ in range(N):
        x, y = map(int, input().split())
        points.append((x, y))
    
    if N == 0:
        print(1.0)
        return
    
    uf = UnionFind(N)
    for i in range(N):
        for j in range(i + 1, N):
            x1, y1 = points[i]
            x2, y2 = points[j]
            dx = x1 - x2
            dy = y1 - y2
            if dx * dx + dy * dy <= 100:  # 10^2
                uf.unite(i, j)
    
    groups = defaultdict(list)
    for i in range(N):
        root = uf.find(i)
        groups[root].append(points[i])
    
    max_candidate = 0.0
    for group in groups.values():
        max_dist_sq = 0
        n = len(group)
        for i in range(n):
            x1, y1 = group[i]
            for j in range(i + 1, n):
                x2, y2 = group[j]
                dx = x1 - x2
                dy = y1 - y2
                dist_sq = dx * dx + dy * dy
                if dist_sq > max_dist_sq:
                    max_dist_sq = dist_sq
        max_dist = math.sqrt(max_dist_sq) if max_dist_sq > 0 else 0.0
        candidate = max_dist + 2.0
        if candidate > max_candidate:
            max_candidate = candidate
    
    ans = max(max_candidate, 1.0)
    print("{0:.9f}".format(ans))

if __name__ == "__main__":
    main()