public static char[] multiplyInterface(char[] number1, char[] number2) {
		number1 = (number1.length==0)?new char[] {'0'}:number1;
		number2 = (number2.length==0)?new char[] {'0'}:number2;
		
		boolean minus = false;
		if(number1[0]=='-' && number2[0]!='-') {
			number1 = Arrays.copyOfRange(number1, 1, number1.length);
			minus = true;
		} else if(number1[0]!='-' && number2[0]=='-') {
			number2 = Arrays.copyOfRange(number2, 1, number2.length);
			minus = true;
		} else if(number1[0]=='-' && number2[0]=='-') {
			number1 = Arrays.copyOfRange(number1, 1, number1.length);
			number2 = Arrays.copyOfRange(number2, 1, number2.length);
		}
		
		char[] result = multiply(number1, number2, minus);
		return result;
	}