#include<bits/stdc++.h>
using namespace std;
int m,i,a[1005],h,n;
float p;
int main(){
	cin>>n>>m;
	for(i=0;i<m;i++){
		cin>>a[i];
	}
	for(i=0;i<m;i++){
		h+=a[i];
	}
	p=h*1.0/m;
	printf("%.1f",p*n);
	return 0;
}

/**************************************************************
	Problem: 1316
	User: zhangziang
	Language: C++
	Result: Accepted
	Time:8 ms
	Memory:2076 kb
****************************************************************/