var factorial = function(n) {
  var result = 1;

  for (var i=n; i>0; i--) {
    result *= i;
  }

  return result;
}

/**
 * @param {number} m
 * @param {number} n
 * @return {number}
 */
var uniquePaths = function(m, n) {
    if (m == 1 || n == 1) {
        return 1;
    }
    else {
        m--;
        n--;

        return factorial(m+n) / (factorial(m) * factorial(n));
    }
}

var uniquePaths1 = function(m, n) {
    var count = 1;

    // This works, but is slow.
    if (m <= 0 || n <= 0) {
        count = 0;
    }
    else {
        if (m === 1 && n === 1) {
            count = 1;
        }
        else if (m === 2 && n === 1) {
            count = 1;
        }
        else if (m === 1 && n === 2) {
            count = 1;
        }
        else if (m === 2 && n === 2) {
            count = 2;
        }

        if (m > 2 || n > 2) {
            for (var x=m; x>0; x--) {
                for (var y=n; y>0; y--) {
                    count += uniquePaths(x - 1, y - 1);
                }
            }
        }
    }

    return count;
};