// Alicia Thorsen
// prime.C
// 1/23/09
//
// Outputs all prime numbers in a range.

#include <iostream>
#include <cstdlib>
using namespace std;

int main() {
  int lower, upper, count = 0;
  char dash;
  bool prime = true;
  cout << "Enter a range of numbers: e.g. 5 - 100: ";
  cin >> lower >> dash >> upper;

  // Valid range.
  if (upper < lower) {
    cout << "You're an idiot." << endl;
    exit(1);
  }

  cout << "Prime numbers between " << lower << " and " << upper << ":" << endl;

  if (lower <= 2 && upper >= 2)
      cout << 2 << " ";

  if (lower < 3) {
    lower = 3;
  }

  // Make lower an odd number.
  if (lower % 2 == 0)
    lower++;

  for (int i = lower; i <= upper; i += 2) {
    prime = true;
    for (int divisor = 3; prime && (divisor < i/2); divisor += 2, ++count) {
      if (i % divisor == 0)
        prime =false;
    }
    if (prime)
      cout << i << " ";
  }
  cout << "\n# of iterations: " << count << endl;
  return 0;
}