const assert = require('assert');

const numbersDict = {
	I: 1, V: 5, X: 10, L: 50, C: 100, D: 500, M: 1000
};

const fromRoman = input => [...input.toUpperCase()].reduce((number, letter, i, source) => number += (numbersDict[letter] >= ( numbersDict[source[i + 1]] | 0)) ? numbersDict[letter] : -numbersDict[letter], 0);

assert.equal(fromRoman('I'), 1, 'I=' + fromRoman('I'));
assert.equal(fromRoman('XI'), 11, 'XI=' + fromRoman('XI'));
assert.equal(fromRoman('XXI'), 21, 'XXI=' + fromRoman('XXI'));
assert.equal(fromRoman('XXVI'), 26, 'XXVI=' + fromRoman('XXVI'));
assert.equal(fromRoman('MMMD'), 3500, 'MMMD=' + fromRoman('MMMD'));

assert.equal(fromRoman('XIX'), 19, 'XIX=' + fromRoman('XIX'));
assert.equal(fromRoman('IV'), 4, 'IV=' + fromRoman('IV'));
assert.equal(fromRoman('IX'), 9, 'IX=' + fromRoman('IX'));
assert.equal(fromRoman('MMCD'), 2400, 'MMCD=' + fromRoman('MMCD'));
assert.equal(fromRoman('MMCM'), 2900, 'MMCM=' + fromRoman('MMCM'));