import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.Scanner;


public class pairE {

	public static void main(String[] args) {
		List<String> inputStrings = getInput();

		for(int i = 0; i < (inputStrings.size() - 1); i++){
			List<Integer> intArrayList = getIntArray(inputStrings.get(i));

			Collections.sort(intArrayList);

			int[][] matrix = createMatrix(intArrayList);

			findSFromMatrix(matrix, intArrayList);
		}
	}
	//Main Algorithm
	private static void findSFromMatrix(int[][] matrix, List<Integer> intArrayList){
		/*
		 * + | 1 2 3 4
		 * ------------
		 * 1 | x 3 4 5
		 * 2 | x x 5 6
		 * 3 | x x x 7
		 * 4 | x x x x
		 */

		List<Integer> matches = new ArrayList<Integer>();

		for(int i = 3; i < intArrayList.size(); i++){
			for(int j = 0; j < i; j++){
				for(int k = 1; k < i; k++){
					if(matrix[j][i] == matrix[j + 1][i - k]){
						matches.add(matrix[j][i]);
						break;
					}
				}
			}
		}

		//System.out.println(matches.toString());

		if(matches.size() == 0){
			System.out.println("None");
		}else{
			Collections.sort(matches);
			System.out.println("yes: " + matches.get(0));
		}
	}

	private static int[][] createMatrix(List<Integer> intArrayList){
		int[][] matrix = new int[intArrayList.size()][intArrayList.size()];

		for(int i = 1; i < intArrayList.size(); i++){
			for(int j = 0; j < i; j++){
				matrix[j][i] = intArrayList.get(i) + intArrayList.get(j);
			}
		}

		return matrix;
	}

	private static List<String> getInput(){
		Scanner scan = new Scanner(System.in);

		List<String> inputStrings = new ArrayList<String>();

		while(scan.hasNext()){
			inputStrings.add(scan.nextLine());

			if(inputStrings.get(inputStrings.size() - 1).equals("0")){
				break;
			}
		}

		scan.close();

		return inputStrings;
	}

	private static List<Integer> getIntArray(String inputString){
		String[] splitString = inputString.split(" ");
		List<Integer> intArrayList = new ArrayList<Integer>();

		for(int i = 0; i < (splitString.length); i++){
			intArrayList.add(Integer.parseInt(splitString[i]));
		}

		return intArrayList;
	}

}