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

main(){
	int i=0,N=0;
    double xa=0.0,ya=0.0,xb=0.0,yb=0.0,a=0.0,b=0.0,sumL=0.0,sumLSQU=0.0,tem1=.0,tem2=.0;
	double tem;
	while(1){
		sumL=0.0;
		sumLSQU=0.0;
		scanf("%d",&N);
		if(N==0) break;
		scanf("%lf%lf%lf%lf",&xa,&ya,&xb,&yb);
		for(i=0;i<N;i++){
			scanf("%lf",&tem);
			sumL=sumL+tem;
			sumLSQU=sumLSQU+tem*tem;
		}
		a=ya/xa;
		b=yb/xb;
		tem1=1.0/(a+1.0)-1.0/(b+1.0);
		tem2=a/(a+1.0)-b/(b+1.0);
		printf("%.3f\n",1.0/1.414213562373095*sumL*sumL/sqrt(tem1*tem1+tem2*tem2)-0.50000*sumLSQU);
	}
}