#include <iostream>
#include <cmath>
#include <numeric>
#include <iterator>
 
using namespace std;
 
template<typename T>
T SumOfSqr(T sum, T a)
{
	return sum + a*a;
}
 
template<typename It1>
double rms2(It1 b, It1 e){
	typedef typename std::iterator_traits<It1>::value_type valueType;
    valueType sum = std::accumulate(b, e, valueType(), SumOfSqr<valueType>);
    return sqrt(sum*0.5);
}
 
int main() {
	std::istream_iterator<int> eos;
	std::istream_iterator<int> it (std::cin);
 
	cout << rms2(it, eos) << endl;
 
	return 0;
}

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