#include <iostream>
#include <cstdlib>

using namespace std;

int main(void)
{
int n;
int k=0;
cin>>n;
double p = 0;
double *x = (double *)malloc(n*sizeof(double));
for(int i=0;i<n;i++)
{
cin>>x[i];
if (x[i]<0)
{
p+=x[i];
k++;
}
}
p/=k;
cout<<p;
}