> #include <iostream.h>
> #include <stdio.h>
> #include<math.h>
> 
> void main(){
> 	int t, n, i;
> 	long double R, PI, k;
> 	PI  = acos(-1);
> 	cin>>t;
> 	for(i=1; i<=t;++i){
> 		cin>>R>>n;
> 		cout<<"Scenario #"<<i<<":"<<endl;
> 		k = PI/n;
> 		k = (sin(k) + sin(PI-k))/2;
> 		k = k/(1+k);
> 		if(n==2) printf("%.3llf\n\n",R/2);
> 		else printf("%.3llf\n\n",R*k);
> 	}
> }