function solve3(input) {
    input.pop();
    let heroes = {};

    for (const line of input) {
        let [command, heroName, spellName] = line.split(' ');

        if (command === 'Enroll') {
            if (heroes[heroName]) {
                console.log(`${heroName} is already enrolled.`);
            } else {
                heroes[heroName] = [];
            }

        } else if (command === 'Learn') {
            if (!heroes[heroName]) {
                console.log(`${heroName} doesn't exist.`);
            } else if (heroes[heroName].includes(spellName)) {
                console.log(`${heroName} has already learnt ${spellName}.`);
            } else {
                heroes[heroName].push(spellName);
            }

        } else if (command === 'Unlearn') {
            if (!heroes[heroName]) {
                console.log(`${heroName} doesn't exist.`);
            } else if (heroes[heroName].includes(spellName)) {
                let index = heroes[heroName].indexOf(spellName);
                heroes[heroName].splice(index, 1);
            } else if (!heroes[heroName].includes(spellName)) {
                console.log(`${heroName} doesn't know ${spellName}.`);
            }
        }
    }

    let heroesArr = Object.entries(heroes);

    function sortHeroes(heroA, heroB) {
        let [nameA, spellA] = heroA;
        let countA = spellA.length;

        let [nameB, spellB] = heroB;
        let countB = spellB.length;

        if (countA === countB) {
            return nameA.localeCompare(nameB);
        } else {
            return countB - countA;
        }
    }

    heroesArr.sort(sortHeroes);

    let sortedHeroes = Object.fromEntries(heroesArr);

    console.log('Heroes:');


    for (const hero in sortedHeroes) {
        let spells = sortedHeroes[hero].join(', ');
        console.log(`== ${hero}: ${spells}`);
    }

}