#include<bits/stdc++.h>
using namespace std;
int main()
{
	int m,n,i;
	float s=0;
	cin>>m>>n;
	int w[10];
	for(i=0;i<n;i++){
		cin>>w[i];
		s+=w[i];
	}
	s/=n;
	s*=m;
	printf("%.1f",s);
	return 0;
}

/**************************************************************
	Problem: 1316
	User: zzz
	Language: C++
	Result: Accepted
	Time:8 ms
	Memory:2072 kb
****************************************************************/