#include <iostream>
#include <fstream>
#include <iomanip>

#include <vector>

#include <cmath>

using namespace std;

double sqr(double n) {
    return n * n;
}

double mean(vector <double> vec) {
    double sum = 0;

    for (size_t i = 0; i < vec.size(); i++) {
        sum += vec[i];
    }

    return sum / vec.size();
}

double variance(vector <double> vec) {
    double m = mean(vec);
    double sumsqr = 0;

    for (size_t i = 0; i < vec.size(); i++) {
        sumsqr += sqr(vec[i]);
    }

    return sumsqr / vec.size() + sqr(m);
}

double RMS(vector <double> vec) {
    return sqrt(variance(vec) + sqr(mean(vec)));
}

double read_vector(vector <double>& vec, char* filename) {
    ifstream input(filename);
    vec.clear();
    double x;

    while (input >> x) {
        vec.push_back(x);
    }
}

int main(int argc, char **argv) {
    if (argc != 3) {
        cout << "Usage: rms <estimator error filename> <true error filename>" << endl;
        return 1;
    }

    vector <double> estim_error, true_error;
    read_vector(estim_error, argv[1]);
    read_vector(true_error, argv[2]);

    if (estim_error.empty() || true_error.empty()) {
        cout << "Files should be non-empty!" << endl;
        return 1;
    }

    if (estim_error.size() != true_error.size()) {
        cout << "Amount of numbers in files must be the same!" << endl;
        return 1;
    }

    vector <double> diff(estim_error.size());
    for (size_t i = 0; i < diff.size(); i++) {
        diff[i] = estim_error[i] - true_error[i];
    }

    cout << setprecision(6) << fixed;
    cout << RMS(diff);

    return 0;
}