1 #include<iostream>
2 #include <math.h>
3 #include <algorithm>
4 #include<stdio.h>
5
6 using namespace std;
7
8 #define eps 1e-8
9 #define zero(x) (((x)>0?(x):-(x))<eps)
10 struct point{ double x, y; }p[100005], convex[100005];
11
12 double xmult(point p1, point p2, point p0)
13 {
14 return (p1.x - p0.x)*(p2.y - p0.y) - (p2.x - p0.x)*(p1.y - p0.y);
15 }
16
17 int dist2(point a, point b)
18 {
19 return (a.x - b.x) * (a.x - b.x) + (a.y - b.y) * (a.y - b.y);
20 }
21
22 point p1, p2;
23 int graham_cp(const void* a, const void* b){
24 double ret = xmult(*((point*)a), *((point*)b), p1);
25 return zero(ret) ? (xmult(*((point*)a), *((point*)b), p2) > 0 ? 1 : -1) : (ret > 0 ? 1 : -1);
26 }
27 void _graham(int n, point* p, int& s, point* ch){
28 int i, k = 0;
29 for (p1 = p2 = p[0], i = 1; i<n; p2.x += p[i].x, p2.y += p[i].y, i++)
30 if (p1.y - p[i].y>eps || (zero(p1.y - p[i].y) && p1.x > p[i].x))
31 p1 = p[k = i];
32 p2.x /= n, p2.y /= n;
33 p[k] = p[0], p[0] = p1;
34 qsort(p + 1, n - 1, sizeof(point), graham_cp);
35 for (ch[0] = p[0], ch[1] = p[1], ch[2] = p[2], s = i = 3; i < n; ch[s++] = p[i++])
36 for (; s>2 && xmult(ch[s - 2], p[i], ch[s - 1]) < -eps; s--);
37 }
38
39 int wipesame_cp(const void *a, const void *b)
40 {
41 if ((*(point *)a).y < (*(point *)b).y - eps) return -1;
42 else if ((*(point *)a).y >(*(point *)b).y + eps) return 1;
43 else if ((*(point *)a).x < (*(point *)b).x - eps) return -1;
44 else if ((*(point *)a).x >(*(point *)b).x + eps) return 1;
45 else return 0;
46 }
47
48 int _wipesame(point * p, int n)
49 {
50 int i, k;
51 qsort(p, n, sizeof(point), wipesame_cp);
52 for (k = i = 1; i < n; i++)
53 if (wipesame_cp(p + i, p + i - 1) != 0) p[k++] = p[i];
54 return k;
55 }
56
57 int graham(int n, point* p, point* convex, int maxsize = 1, int dir = 1){
58 point* temp = new point[n];
59 int s, i;
60 n = _wipesame(p, n);
61 _graham(n, p, s, temp);
62 for (convex[0] = temp[0], n = 1, i = (dir ? 1 : (s - 1)); dir ? (i < s) : i; i += (dir ? 1 : -1))
63 if (maxsize || !zero(xmult(temp[i - 1], temp[i], temp[(i + 1) % s])))
64 convex[n++] = temp[i];
65 delete[]temp;
66 return n;
67 }
68
69 int rotating_calipers(point *ch, int n)
70 {
71 int q = 1, ans = 0;
72 ch[n] = ch[0];
73 for (int p = 0; p < n; p++)
74 {
75 while (xmult(ch[p + 1], ch[q + 1], ch[p]) > xmult(ch[p + 1], ch[q], ch[p]))
76 q = (q + 1) % n;
77 ans = max(ans, max(dist2(ch[p], ch[q]), dist2(ch[p + 1], ch[q + 1])));
78 }
79 return ans;
80 }
81 int main()
82 {
83 int n;
84 cin >> n;
85 for (int i = 0; i < n; i++)
86 {
87 scanf("%lf%lf", &p[i].x, &p[i].y);
88 }
89 int size = graham(n, p, convex, 1, 0);
90 //cout << rotating_calipers(convex, size) << endl;
91 printf("%.8lf\n",sqrt(rotating_calipers(convex, size)));
92 return 0;
93 }
