// Program: ex1a_template.cpp
// Author: ...

#include <iostream>
#include <cassert>

// PRE: [begin, end) is a valid non-empty range.
// POST: returns the average of the elements in [begin, end)
double average (const double* begin, const double* end)
{
  // [Your code ...]
}

int main ()
{
  // Input numbers
  const unsigned int len = 20;
  double a[len];
  std::cout << "Input " << len << " numbers: ";
  for (double* i = a; i < a+len; ++i)
    std::cin >> *i;
  
  // Output average
  std::cout << "Average = " << average(a, a+len) << "\n";
  
  return 0;
}