#include <iostream.h> #include <stdio.h> #include <fstream.h> #include <math.h> ifstream f("pi.in"); #define cin f int fun(int m,int n) { int q; q=m%n; while(q!=0) { m=n; n=q; q=m%n; } return n; } int main() {     int n,i,j;     int a[51];     while(cin>>n)     {         int sum=0;         if (n==0) return 0;         for(i=0;i<n;i++)         cin>>a[i];         for(i=0;i<n;i++)         for(j=i+1;j<n;j++)         {             int x=a[i];             int y=a[j];             if (fun(x,y)==1) sum++;         }         if(sum==0)         cout<<"No estimate for this data set.\n";         else         printf("%0.6f\n",sqrt(6*n*(n-1)/2/sum));     } } 

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