function hero(input){

    let obj={};


    for(let line of input){
        let [command,name,spell]=line.split(" ");
        if(command==="End"){
            break;
        }else if(command==="Enroll"){
            if(!obj.hasOwnProperty(name)){
                obj[name]=[];
            }else {
                console.log(`${name} is already enrolled.`)
            }

        }else if(command==="Learn"){
            if(!obj.hasOwnProperty(name)){
                console.log(`${name} doesn't exist.`);
            }else if(!obj[name].includes(spell)){
                obj[name].push(spell);
            }else if(obj[name].includes(spell)){
                console.log(`${name} has already learnt ${spell}.`);
            }

        }else if(command==="Unlearn"){
            if(!obj.hasOwnProperty(name)){
                console.log(`${name} doesn't exist.`);
            }else if(obj[name]===undefined || !obj[name].includes(spell) ){
                console.log(`${name} doesn't know ${spell}.`);
            }else if(obj[name].includes(spell)){
                obj[name].splice(obj[name].indexOf(spell),1);
            }

        }
    }
    let sorted=Object.entries(obj).sort((a,b)=>b[1].length-a[1].length || a[0].localeCompare(b[0]));
    console.log(`Heroes:`);
    for(let kvp of sorted){
        console.log(`== ${kvp[0]}: ${kvp[1]}`);
    }


}