#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <math.h>

#define MAXN 25000

int n;

typedef struct {
	int x, y;
} coord;

coord a[MAXN];

void generate1(void)
{
	int i;
	n = MAXN;
	for (i = 0; i < n; i++) {
		a[i].x = ((int) rand()%20000) - 10000;
		a[i].y = ((int) rand()%20000) - 10000;
	}
}

double dist(coord a, coord b)
{
	return sqrt(fabs((a.x - b.x) * (a.x - b.x)) + fabs((a.y - b.y) * (a.y - b.y)));
}

double DoWork(coord a[], int n)
{
	double mdist = 0.0;
	int i, j;
	for (i = 0; i < n; i++)
		for (j = 0; j < n; j++) 
			if (dist(a[i], a[j]) > mdist)  {
				mdist = dist(a[i], a[j]);
			}
	return mdist;
}

int main(void)
{
	generate1();
	unsigned clk0 = clock();
	printf("%.4lf\n", DoWork(a, n));
	printf("Time elapsed: %d milliseconds\n", (clock() - clk0) / 1000);
	return 0;
}