UVA 412 Pi

/***
	Md. Nazmul Hasan
	Shahjalal University of Science & Technology,Sylhet.
	hasan08sust@gmail.com
	***/
	#include<iostream>
	#include<cstdio>
	#include<stack>
	#include<queue>
	#include<map>
	#include<vector>
	#include<algorithm>
	#include<cstring>
	#include<sstream>
	#include<cmath>
	#include <iomanip>
	using namespace std ;
	typedef long long ll ;
	typedef int in ;
	typedef unsigned long long ull ;
	const double pi = 2*acos(0) ;
	#define maxi 40000
	#define pf printf
	#define sc scanf
	#define pb push_back
	#define MEM(x,y) (memset((x),(y),sizeof(x)))
	#define MIN(x,y) ((x) < (y) ? (x) : (y))
	#define MAX(x,y) ((x) > (y) ? (x) : (y))
	#define load(array,size) for(int i=0 ; i<size ; i++) cin>>array[i] ;
	#define new_line pf("\n")
	#define clear_data(array) memset(array,0,sizeof(array))
	#define highest_int 2147483647
	int GCD(int a, int b)
	{
	if(a%b==0) return b;
	return GCD(b,a%b);
	}
	int main()
	{
	int n,m,p,cnt,a,b,d;
	vector<int>data;
	while(sc("%d",&n))
	{
	if(n<=1 || n>=50)
	break;
	m = n-1;
	cnt =0 ;
	int total = m*(m+1)/2;
	for(int i=0 ; i<n ; i++)
	{
	sc("%d",&p);
	data.pb(p);
	}
	for(int i=0 ; i<data.size()-1 ; i++)
	{
	//j = i+1;
	for(int j = i+1 ; j<data.size() ; j++)
	{
	a = data[i];
	b = data[j];
	d = GCD(a,b);
	if(d==1)
	{
	cnt++;
	//pf("-> %d %d\n",a,b);
	}
	}
	}
	if(cnt==0)
	{
	pf("No estimate for this data set.\n");
	}
	else
	{
	double val = (6*total*1.0)/cnt ;
	double pi = sqrt(val);
	pf("%.6lf\n",pi);
	}
	data.clear();
	}
	return 0;
	}