#include <iostream>
#include <iomanip>
using namespace std;

int main() {
    int m, n;
    cin >> m >> n;  // 读取橘子总数和抽样个数

    double sum = 0.0;
    for (int i = 0; i < n; ++i) {
        double weight;
        cin >> weight;  // 读取每个抽样橘子的重量
        sum += weight;  // 累加总重量
    }

    double average = sum / n;  // 计算平均重量
    double total = m * average;  // 计算整箱大约总重量

    // 设置输出精度为1位小数
    cout << fixed << setprecision(1) << total << endl;

    return 0;
}
/**************************************************************
	Problem: 1316
	User: mc002
	Language: C++
	Result: Accepted
	Time:6 ms
	Memory:2072 kb
****************************************************************/