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

/**************************************************************
	Problem: 1316
	User: wtq001
	Language: C++
	Result: Accepted
	Time:9 ms
	Memory:2072 kb
****************************************************************/