text: /**
   * Write a function that sums the numbers from 1 to n, but only multiples
   * of three or five are considered in the sum,
   * e.g. 3, 5, 6, 9, 10, 12, 15 for n=17
   *
   * n cannot be negative in this excersise.
   */
  var Sum = function() {
    'use strict';
  
    function sumNumbers35(n) {
  
    	if (n < 0) {
    		throw 'No negative numbers allowed';
    	}
  
    	for (var i = 0, sum = 0; i <= n; i++) {
    		if (i % 3 === 0 || i % 5 === 0) {
    			sum += i;
    		}
    	}
  
    	return sum ;
  
    }
  
    return {
      sumNumbers: sumNumbers35
    };
  };