#include<stdio.h>
int main()
{
	int i,N,v[100],a,j;
	float sum=0.0;
	scanf("\n%d",&N);
	for (i=0;i<N;i++)
	{
		scanf("%d",&v[i]);
	}


	for (i=0;i<N-1;i++) 
	{
		for(j=0;j<N-i-1;j++)
		{
			if( v[j]>v[j+1] )
			{	a=v[j];
				v[j] = v[j+1];
				v[j+1]=a;
			}
		}
	}

        sum= (float) a[0]/2+a[1]/2;
	if(N>2)
	{
	for(i=2;i<N;i++)
	{
		sum = sum/2 + (float)v[i]/2;
	}
	}
	printf("\n%f",sum);
	return 0;
}


