#include <iostream>

using std::cout;
using std::cin;
using std::endl;

#include <cmath>

float StandardDeviation(float a[], int n);

int main(){

  int n = 0;
  
  cout<<"Insert n : "<<endl;
  cin>>n;

  const int dim = n;
  float a[dim] = {0};

  cout<<"Insert the values "<<endl;

  for(int i = 0; i < n; i++)
    cin>>a[i];
  
  cout<<"Standard deviation: "<<StandardDeviation(a,n)<<endl;

  return 0;
}

float StandardDeviation(float a[], int n){

  float sum;
  float mean;
  float stdev;
  float dev;

  if(n>=0){

    for(int i = 0; i < n ; i++){
      sum += a[i];
    }

    mean = sum/n;
        
    for(int i = 1; i < n; i++){
      dev = a[i]-mean;
      sum+=dev*dev;
    }
  }
  return sqrt(sum/(n-1));
}