(function main() {
  var prompt = require('prompt');

  function gcd(a,b) {
    return ((b==0) ? a : gcd(b,a%b));
  }

  prompt.start()

  prompt.get(['a','b'], function(err,result) {
    try {

      var input = {
        'a' : parseInt(result.a),
        'b' : parseInt(result.b)
      }

      var errors = (function() {
        for (var i in input) {
          if (isNaN(input[i])) {
            throw new Error('The value entered for '+i+' is not a number!')
          }
        }
        return false;
      })();

      console.log('GCD is: '+gcd(input['a'],input['b']));

    } catch(err) {
      console.log("Had an error parsing your input: "+err);
    }
  });
})();