let size = +prompt("Укажите размер верхней одежды:","");
const usaSizeText = 'для США -';
const italySizeText = 'для Италии -';

switch (size) {
	case 40:
		alert(`${usaSizeText} 6, ${italySizeText} 38`);
		break;
	case 42:
		alert(`${usaSizeText} 8, ${italySizeText} 40`);
		break;
	case 44:
		alert(`${usaSizeText} 10, ${italySizeText} 42`);
		break;
	case 46:
		alert(`${usaSizeText} 12, ${italySizeText} 44`);
		break;
	case 48:
		alert(`${usaSizeText} 14, ${italySizeText} 46`);
		break;
	case 50:
		alert(`${usaSizeText} 16, ${italySizeText} 48`);
		break;
	case 52:
		alert(`${usaSizeText} 18, ${italySizeText} 50`);
		break;
	case 54:
		alert(`${usaSizeText} 20, ${italySizeText} 52`);
		break;
	default:
		alert('Вы указали неверный размер.');
}