#include <iostream>
#include <iomanip>

int main() {
    int m, n;
    std::cin >> m >> n;

    int totalWeightOfN = 0;
    int weight;
    for (int i = 0; i < n; ++i) {
        std::cin >> weight;
        totalWeightOfN += weight;
    }

    double averageWeight = static_cast<double>(totalWeightOfN) / n;
    double totalWeightOfM = averageWeight * m;

    std::cout << std::fixed << std::setprecision(1) << totalWeightOfM << std::endl;

    return 0;
}
/**************************************************************
	Problem: 1316
	User: panyuchen
	Language: C++
	Result: Accepted
	Time:8 ms
	Memory:2072 kb
****************************************************************/