#include<bits/stdc++.h>
using namespace std;
int main(){
	int  m,n,a[100]={},i;
	float h;
	cin>>m>>n;
	for(i=0;i<n;i++){
		cin>>a[i];
	}
	for(i=0;i<n;i++){
		h=h+a[i];
	}
	h=h/n*m;
	printf("%.1f",h);
	return 0;
}
/**************************************************************
	Problem: 1316
	User: caiqiaoxi
	Language: C++
	Result: Accepted
	Time:7 ms
	Memory:2072 kb
****************************************************************/