#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: linmiaoling
	Language: C++
	Result: Accepted
	Time:11 ms
	Memory:2072 kb
****************************************************************/