Problem: Ksenia has an array a consisting of n positive integers a_1, a_2, …, a_n. 

In one operation she can do the following: 

  * choose three distinct indices i, j, k, and then 
  * change all of a_i, a_j, a_k to a_i ⊕ a_j ⊕ a_k simultaneously, where ⊕ denotes the [bitwise XOR operation](https://en.wikipedia.org/wiki/Bitwise_operation#XOR). 



She wants to make all a_i equal in at most n operations, or to determine that it is impossible to do so. She wouldn't ask for your help, but please, help her!

Input

The first line contains one integer n (3 ≤ n ≤ 10^5) — the length of a.

The second line contains n integers, a_1, a_2, …, a_n (1 ≤ a_i ≤ 10^9) — elements of a.

Output

Print YES or NO in the first line depending on whether it is possible to make all elements equal in at most n operations.

If it is possible, print an integer m (0 ≤ m ≤ n), which denotes the number of operations you do.

In each of the next m lines, print three distinct integers i, j, k, representing one operation. 

If there are many such operation sequences possible, print any. Note that you do not have to minimize the number of operations.

Examples

Input


5
4 2 1 7 2


Output


YES
1
1 3 4

Input


4
10 4 49 22


Output


NO

Note

In the first example, the array becomes [4 ⊕ 1 ⊕ 7, 2, 4 ⊕ 1 ⊕ 7, 4 ⊕ 1 ⊕ 7, 2] = [2, 2, 2, 2, 2].

Solution (in JAVA):

Solution:
import java.util.*;

import javax.swing.text.Utilities;

import java.io.*;

public class A2oj2 {

    static FastReader sc;
    static PrintWriter out;
    static int mod = 1000000007;

    public static void main(String[] args) throws IOException {
        if (System.getProperty("ONLINE_JUDGE") == null) {
            File f1 = new File("input.txt");
            File f2 = new File("output.txt");
            Reader r = new FileReader(f1);
            sc = new FastReader(r);
            out = new PrintWriter(f2);
            double prev = System.currentTimeMillis();
            solve();
            out.println("\n\nExecuted in : " + ((System.currentTimeMillis() - prev) / 1e3) + " sec");
        } else {
            sc = new FastReader(new InputStreamReader(System.in));
            out = new PrintWriter(System.out);
            solve();
        }
        out.flush();
        out.close();
    }

    static void solve() {
        // int t = sc.nextInt();
        // StringBuilder ans = new StringBuilder("");
        // while (t-- > 0) {

        // }
        // out.println(ans);
        int n = sc.nextInt();
        int[] arr = new int[n];
        for (int i = 0; i < n; i++) {
            arr[i] = sc.nextInt();
            if (i > 0)
                arr[i] ^= arr[i - 1];
        }
        if (n % 2 == 0) {
            n--;
            if (arr[n] != 0) {
                out.println("NO");
                return;
            }
        }
        out.println("YES\n" + (n - 2));
        for (int i = 1; i < n; i += 2) {
            out.println(i + " " + (i + 1) + " " + (i + 2));
        }
        for (int i = 1; i < n - 2; i += 2) {
            out.println(i + " " + (i + 1) + " " + n);
        }
    }

    static boolean isPrime(long n) {
        if (n % 2 == 0)
            return false;
        for (int i = 3; i * i <= n; i += 2) {
            if (n % i == 0)
                return false;
        }
        return true;
    }

    static long modInverse(long a) {
        long g = gcd(a, mod);
        if (g != 1)
            return -1;
        else {
            return modPower(a, mod - 2L);
        }
    }

    static long modPower(long x, long y) {
        long res = 1;
        x = x % mod;
        if (x == 0)
            return 0;
        while (y > 0) {
            if ((y & 1) != 0)
                res = (res * x) % mod;
            y = y >> 1;
            x = (x * x) % mod;
        }
        return res;
    }

    static long gcd(long a, long b) {
        if (b == 0)
            return a;
        else
            return gcd(b, a % b);
    }

    static boolean isPerfectSquare(long x) {
        long sqrt = (long) Math.sqrt(x);
        return (sqrt * sqrt) == x;
    }

    public static int digitsCount(long x) {
        return (int) Math.floor(Math.log10(x)) + 1;
    }

    public static boolean isPowerTwo(long n) {
        return (n & n - 1) == 0;
    }

    static void sieve(boolean[] prime, int n) { // Sieve Of Eratosthenes
        for (int i = 1; i <= n; i++) {
            prime[i] = true;
        }
        for (int i = 2; i * i <= n; i++) {
            if (prime[i]) {
                for (int j = 2; i * j <= n; j++) {
                    prime[i * j] = false;
                }
            }
        }
    }

    static long nCr(int n, int r) { // Combinations
        if (n < r)
            return 0;
        if (r > n - r) { // because nCr(n, r) == nCr(n, n - r)
            r = n - r;
        }
        long ans = 1L;
        for (int i = 0; i < r; i++) {
            ans *= (n - i);
            ans /= (i + 1);
        }
        return ans;
    }

    static long catalan(int n) { // n-th Catalan Number
        long c = nCr(2 * n, n);
        return c / (n + 1);
    }

    static class Pair implements Comparable<Pair> { // Pair Class
        int x;
        int y;

        public Pair(int x, int y) {
            this.x = x;
            this.y = y;
        }

        @Override
        public boolean equals(Object o) {
            if (this == o) {
                return true;
            }
            if (!(o instanceof Pair)) {
                return false;
            }

            Pair pair = (Pair) o;

            if (x != pair.x) {
                return false;
            }
            if (y != pair.y) {
                return false;
            }

            return true;
        }

        @Override
        public int hashCode() {
            long result = x;
            result = 31 * result + y;
            return (int) result;
        }

        @Override
        public int compareTo(Pair o) {
            return (int) (this.x - o.x);
        }
    }

    static class Trip { // Triplet Class
        long x;
        long y;
        long z;

        Trip(long x, long y, long z) {
            this.x = x;
            this.y = y;
            this.z = z;
        }

        @Override
        public boolean equals(Object o) {
            if (this == o) {
                return true;
            }
            if (!(o instanceof Trip)) {
                return false;
            }

            Trip trip = (Trip) o;

            if (x != trip.x) {
                return false;
            }
            if (y != trip.y) {
                return false;
            }
            if (z != trip.z) {
                return false;
            }
            return true;
        }

        @Override
        public int hashCode() {
            long result = 62 * x + 31 * y + z;
            return (int) result;
        }
    }

    static class FastReader {
        BufferedReader br;
        StringTokenizer st;

        public FastReader(Reader r) {
            br = new BufferedReader(r);
        }

        String next() {
            while (st == null || !st.hasMoreElements()) {
                try {
                    st = new StringTokenizer(br.readLine());
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            return st.nextToken();
        }

        int nextInt() {
            return Integer.parseInt(next());
        }

        long nextLong() {
            return Long.parseLong(next());
        }

        double nextDouble() {
            return Double.parseDouble(next());
        }

        int[] readArrayI(int n) {
            int[] arr = new int[n];
            for (int i = 0; i < n; i++) {
                arr[i] = sc.nextInt();
            }
            return arr;
        }

        long[] readArrayL(int n) {
            long[] arr = new long[n];
            for (int i = 0; i < n; i++) {
                arr[i] = sc.nextLong();
            }
            return arr;
        }

        String nextLine() {
            String str = "";
            try {
                str = br.readLine();
            } catch (IOException e) {
                e.printStackTrace();
            }
            return str;
        }
    }

    /*
     * ASCII Range--->(A-Z)--->[65,90]<<::>>(a-z)--->[97,122]
     */
    /******************************************************************************************************************/
    static void printArray(int[] arr) {
        out.print("[");
        for (int i = 0; i < arr.length; i++) {
            if (i < arr.length - 1)
                out.print(arr[i] + ",");
            else
                out.print(arr[i]);
        }
        out.print("]");
        out.println();
    }

    static void printArray(long[] arr) {
        out.print("[");
        for (int i = 0; i < arr.length; i++) {
            if (i < arr.length - 1)
                out.print(arr[i] + ",");
            else
                out.print(arr[i]);
        }
        out.print("]");
        out.println();
    }

    static void printArray(double[] arr) {
        out.print("[");
        for (int i = 0; i < arr.length; i++) {
            if (i < arr.length - 1)
                out.print(arr[i] + ",");
            else
                out.print(arr[i]);
        }
        out.print("]");
        out.println();
    }
    /**********************************************************************************************************************/
}