#include <iostream>
#include <iomanip>
using namespace std;

int main(){
	int a[20];
	int m,n,i;
	double s = 0.0;
	cin>>m>>n;
	
	for(i = 0;i < n;i++){
		cin>>a[i];
		s = s + a[i];
	}
	
	s = s / n;
	s = s * m;
	
	cout<<fixed<<setprecision(1)<<s<<endl;
}
/**************************************************************
	Problem: 1316
	User: admin
	Language: C++
	Result: Accepted
	Time:8 ms
	Memory:2072 kb
****************************************************************/