function calcArea(a, b, c, d) {
    const s = (a + b + c + d) / 2;
    const T = Math.sqrt((s-a)*(s-b)*(s-c)*(s-d));
    return T;
}
 
console.log(process.argv.length)
 
if(process.argv.length !== 6) {
    console.error('Hiba! 4 számot meg kell adni');
    process.exit(1);
}
 
const a = Number(process.argv[2]);
const b = Number(process.argv[3]);
const c = Number(process.argv[4]);
const d = Number(process.argv[5]);

console.log('Terület: ', calcArea(a, b, c, d));