public class Main {
		public static void main(String[] args) throws Exception {
			System.out.println(decToBin(0));
			System.out.println(decToBin(1));
			System.out.println(decToBin(2));
			System.out.println(decToBin(127));
		}
	
		public static String decToBin(int dec) {
			if (dec == 0) {
				return "0"; // special case
			}
	
			final StringBuilder result = new StringBuilder();
			int current = dec;
	
			while (current != 0) {
				result.append(current & 0x1);
				current = current >> 1;
			}
	
			return result.reverse().toString();
		}
	}