toto tam mam..
System.out.print("čitateľ : ");
Scanner citatel = new Scanner(System.in);
int c = citatel.nextInt();
System.out.print("menovatel : ");
Scanner menovatel = new Scanner(System.in);
int m = menovatel.nextInt();
int gcd = gcd (c, m);
c /= gcd;
m /= gcd;


System.out.println(c + "/" + m);

}
}