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 java.lang.*;
import java.io.*;
import java.awt.Point;

// U KNOW THAT IF THIS DAY WILL BE URS THEN NO ONE CAN DEFEAT U HERE................
// ASCII = 48 + i ;// 2^28 = 268,435,456  > 2* 10^8 // log 10 base 2 = 3.3219 
// odd:: (x^2+1)/2 , (x^2-1)/2 ; x>=3// even:: (x^2/4)+1 ,(x^2/4)-1  x >=4 
// FOR ANY ODD NO N : N,N-1,N-2
//ALL ARE PAIRWISE COPRIME 
//THEIR COMBINED LCM IS PRODUCT OF ALL THESE NOS

// two consecutive odds are always coprime to each other
// two consecutive even have always gcd  = 2 ;



public class Main
{
     
    // static int[] arr = new int[100002] ; 
    // static int[] dp = new int[100002] ;  
    
     static PrintWriter out;
    
	static class FastReader{
		BufferedReader br;
		StringTokenizer st;
		public FastReader(){
			br=new BufferedReader(new InputStreamReader(System.in));
			out=new PrintWriter(System.out);
		}
		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());
		}
		String nextLine(){
			String str = "";
			try{
				str=br.readLine();
			}
			catch(IOException e){
				e.printStackTrace();
			}
			return str;
		}
	}
	


////////////////////////////////////////////////////////////////////////////////////
 public static int countDigit(long n) 
    { 
        return (int)Math.floor(Math.log10(n) + 1); 
    } 

///////////////////////////////////////////////////////////////////////////////////////// 
 
 public static int sumOfDigits(long n)
 {
  
  if( n< 0)return -1 ;
  
  int sum = 0;
  
  while( n > 0)
  {
      sum = sum + (int)( n %10) ;
      
      n /= 10 ;
  }
     
  return sum ;  
 
 
 
 }
 
 //////////////////////////////////////////////////////////////////////////////////////////////////

public static long arraySum(int[] arr , int start , int end)
{
    long ans = 0 ;
    
    for(int i = start ; i <= end  ; i++)ans += arr[i] ;
    
    return ans  ;
}

/////////////////////////////////////////////////////////////////////////////////

public static int mod(int x)
{
      if(x <0)return -1*x ;
      else return x ;
}
public static long mod(long x)
{
      if(x <0)return -1*x ;
      else return x ;
}

////////////////////////////////////////////////////////////////////////////////

public static void swapArray(int[] arr , int start , int end)
{
    while(start < end)
    {
        int temp = arr[start] ;
        arr[start] = arr[end];
        arr[end] = temp;
        start++ ;end-- ;
    }
}


//////////////////////////////////////////////////////////////////////////////////

static long factorial(long a)
{
    if(a== 0L || a==1L)return 1L ;
    
    return a*factorial(a-1L) ;
}

///////////////////////////////////////////////////////////////////////////////


public static int[][] rotate(int[][] input){

int n =input.length;
int m = input[0].length ;
int[][] output = new int [m][n];

for (int i=0; i<n; i++)
	for (int j=0;j<m; j++)
		output [j][n-1-i] = input[i][j];
return output;
}
///////////////////////////////////////////////////////////////////////////////////////////////////////

public static int countBits(long n) 
    {  
        int count = 0; 
        while (n != 0) 
        { 
            count++; 
            n = (n) >> (1L) ;
        } 
          
        return count;   
        
    } 
/////////////////////////////////////////// ////////////////////////////////////////////////   

public static boolean isPowerOfTwo(long n) 
{ 
    if(n==0) 
    return false; 
  
if(((n ) & (n-1)) == 0 ) return true ;
else return false  ;

} 

/////////////////////////////////////////////////////////////////////////////////////

 
/////////////////////////////////////////////////////////////////////////////////// 

public static String reverse(String input)
{
  StringBuilder str  = new StringBuilder("") ;
   
    for(int i =input.length()-1 ; i >= 0  ; i-- )
    {
        str.append(input.charAt(i));
    }
    
return str.toString() ;
}
///////////////////////////////////////////////////////////////////////////////////////////

public static boolean sameParity(long a  ,long b )
{
     long x = a% 2L; long y = b%2L ;
     if(x==y)return true  ;
     else return false  ;
}


////////////////////////////////////////////////////////////////////////////////////////////////////
public static boolean isPossibleTriangle(int a  ,int b , int c)
{
      if( a + b > c && c+b > a && a +c > b)return true  ;
      else return false  ;
}


////////////////////////////////////////////////////////////////////////////////////////////
static long xnor(long num1, long num2) {
		if (num1 < num2) {
			long temp = num1;
			num1 = num2;
			num2 = temp;
		}
		num1 = togglebit(num1);
		return num1 ^ num2;
	}

	static long togglebit(long n) {
		if (n == 0)
			return 1;
		long i = n;
		n |= n >> 1;
		n |= n >> 2;
		n |= n >> 4;
		n |= n >> 8;
		n |= n >> 16;
		return i ^ n;
	}

///////////////////////////////////////////////////////////////////////////////////////////////

public static int xorOfFirstN(int n)
{
 
 
 if( n % 4 ==0)return n ;
 
 else if( n % 4 == 1)return 1 ;
 
 else if( n % 4 == 2)return n+1 ;
 
 else return 0 ;
 
    
}
//////////////////////////////////////////////////////////////////////////////////////////////

public static int gcd(int a, int b )
{

if(b==0)return a ;

else return gcd(b,a%b) ; 

}


public static long gcd(long a, long b )
{

if(b==0)return a ;

else return gcd(b,a%b) ; 

}

////////////////////////////////////////////////////////////////////////////////////

public static int lcm(int a, int b ,int c , int d )
{

int temp = lcm(a,b , c) ;


 
 int ans = lcm(temp ,d ) ;

return ans  ;


}

///////////////////////////////////////////////////////////////////////////////////////////

public static int lcm(int a, int b ,int c )
{

int temp = lcm(a,b) ;

int ans =  lcm(temp ,c) ;

return ans  ;


}

////////////////////////////////////////////////////////////////////////////////////////
    
public static int lcm(int a , int b )
{

int gc = gcd(a,b);

return (a*b)/gc ;
}


public static long lcm(long a , long b )
{

long gc = gcd(a,b);

return (a*b)/gc ;
}


///////////////////////////////////////////////////////////////////////////////////////////
static boolean isPrime(long n)
{
      if(n==1)
      {
            return false  ;
      }
      
      boolean ans =  true  ;
      
      for(long i = 2L; i*i <= n ;i++)
      {
            if(n% i ==0)
            {
                  ans = false  ;break ;
            }
      }
      
      
      return ans  ;
} 

static boolean isPrime(int n)
{
      if(n==1)
      {
            return false  ;
      }
      
      boolean ans =  true  ;
      
      for(int i = 2; i*i <= n ;i++)
      {
            if(n% i ==0)
            {
                  ans = false  ;break ;
            }
      }
      
      
      return ans  ;
}      


///////////////////////////////////////////////////////////////////////////

static int sieve =  1000000 ;

 
static boolean[] prime =  new boolean[sieve + 1] ;

public static void sieveOfEratosthenes() 
    { 
        // FALSE == prime
        
        // TRUE ==  COMPOSITE
        
        // FALSE== 1
       
        
        // time complexity = 0(NlogLogN)== o(N)
        
        // gives prime nos bw 1 to N
        
        for(int i = 4; i<= sieve ; i++)
        {
            prime[i] = true  ;
            i++ ;
        }
        
        for(int p = 3; p*p <= sieve; p++) 
        { 
           
            if(prime[p] == false) 
            { 
                
                for(int i = p*p; i <= sieve; i += p) 
                    prime[i] = true; 
            } 
            
            p++ ;
        } 
          
       
       
    
    } 
 
///////////////////////////////////////////////////////////////////////////////////


public static void sortD(int[] arr , int s  , int e)
{
      sort(arr ,s , e) ;
      
      int i =s ; int j = e  ;
      
      while( i < j)
      {
            int temp = arr[i] ;
            arr[i] =arr[j] ;
            arr[j] = temp ;
            i++ ; j-- ;
      }
      
      
      
      return ;
}


/////////////////////////////////////////////////////////////////////////////////////////

public static long countSubarraysSumToK(long[] arr ,long sum )
    {
      HashMap<Long,Long> map = new HashMap<>() ;
       
      int n = arr.length ;
       
      long prefixsum = 0 ;
       
      long count = 0L ;
      for(int i  = 0; i < n ; i++)
      {
          prefixsum  = prefixsum +  arr[i] ;
           
          if(sum == prefixsum)count = count+1 ;
           
          if(map.containsKey(prefixsum -sum))
          {
              count = count + map.get(prefixsum -sum) ;
          }
          
          
          if(map.containsKey(prefixsum ))
          {
              map.put(prefixsum , map.get(prefixsum) +1 );
          }
          
          else{
              map.put(prefixsum , 1L );
          }
           
           
      }
        
        
        
      return count  ;  
        
    }

///////////////////////////////////////////////////////////////////////////////////////////////


// KMP ALGORITHM : TIME COMPL:O(N+M) 
// FINDS THE OCCURENCES OF PATTERN AS A  SUBSTRING IN STRING
//RETURN THE ARRAYLIST OF INDEXES 
// IF SIZE OF LIST IS ZERO MEANS PATTERN IS NOT PRESENT IN STRING


public static ArrayList<Integer> kmpAlgorithm(String str , String pat)
     {
        ArrayList<Integer> list =new ArrayList<>();
        
        int n = str.length() ;
        int m = pat.length() ;
        
        String q = pat + "#" + str ;
        
        int[] lps  =new int[n+m+1] ;
        
         longestPefixSuffix(lps, q,(n+m+1)) ;
         
         
         for(int i =m+1 ; i < (n+m+1) ; i++ )
         {
             if(lps[i] == m)
             {
                 list.add(i-2*m) ;
             }
         }
        
        return list ; 
         
        
    }
    

public static void longestPefixSuffix(int[] lps ,String str , int n)
    {
        lps[0] =  0 ;
        
        for(int i = 1  ; i<= n-1; i++)
        {
          int l = lps[i-1] ;
           
          while( l > 0 && str.charAt(i) != str.charAt(l))
          {
              l = lps[l-1] ;
          }
           
          if(str.charAt(i) == str.charAt(l))
          {
              l++ ;
          }
            
           
          lps[i] = l ; 
        }
        
    }
    
     

///////////////////////////////////////////////////////////////////////////////////////////////////
///////////////////////////////////////////////////////////////////////////////////////////////////

 // CALCULATE TOTIENT Fn FOR ALL VALUES FROM 1 TO n
    // TOTIENT(N) = count of nos less than n and grater than 1 whose gcd with n is 1 
    // or n and the no  will be coprime in nature
    //time : O(n*(log(logn)))
    
    public static void eulerTotientFunction(int[] arr ,int n )
    {
      
      for(int i = 1; i <= n  ;i++)arr[i] =i  ;
      
      
      for(int i= 2 ; i<= n ;i++)
      {
          if(arr[i] == i)
          {
              arr[i] =i-1 ;
              
              for(int j =2*i ; j<= n  ; j+= i )
              {
                  arr[j] = (arr[j]*(i-1))/i ;
              }
              
          }
      }
        
      return  ;  
        
    }
	
/////////////////////////////////////////////////////////////////////////////////////////////
public static long nCr(int n,int k)
{
    long ans=1L;
    k=k>n-k?n-k:k;
    int j=1;
    for(;j<=k;j++,n--)
    {
        if(n%j==0)
        {
            ans*=n/j;
        }else
        if(ans%j==0)
        {
            ans=ans/j*n;
        }else
        {
            ans=(ans*n)/j;
        }
    }
    return ans;
}

///////////////////////////////////////////////////////////////////////////////////////////

public static ArrayList<Integer> allFactors(int n)
{   
      ArrayList<Integer> list = new ArrayList<>() ;
      
    for(int i = 1; i*i <= n ;i++)
    {
          if( n % i == 0)
          {
              if(i*i == n)
              {
                    list.add(i) ;
              }
              else{
                    list.add(i) ;
                    list.add(n/i) ;
                    
              }
          }
    }
      
     return list ; 
      
      
}


public static ArrayList<Long> allFactors(long n)
{   
      ArrayList<Long> list = new ArrayList<>() ;
      
    for(long i = 1L; i*i <= n ;i++)
    {
          if( n % i == 0)
          {
              if(i*i == n)
              {
                    list.add(i) ;
              }
              else{
                    list.add(i) ;
                    list.add(n/i) ;
                    
              }
          }
    }
      
     return list ; 
      
      
}
////////////////////////////////////////////////////////////////////////////////////////////////////

  static final int MAXN = 1000001; 
       
    
    static int spf[] = new int[MAXN]; 
   
    static void sieve() 
    { 
        spf[1] = 1; 
        for (int i=2; i<MAXN; i++) 
       
           
            spf[i] = i; 
       
       
        for (int i=4; i<MAXN; i+=2) 
            spf[i] = 2; 
       
        for (int i=3; i*i<MAXN; i++) 
        { 
           
            if (spf[i] == i) 
            { 
               
                for (int j=i*i; j<MAXN; j+=i) 
       
                    if (spf[j]==j) 
                        spf[j] = i; 
            } 
        } 
    } 
       
// The above code works well for n upto the order of 10^7.
// Beyond this we will face memory issues.

// Time Complexity: The precomputation for smallest prime factor is done in O(n log log n)
// using sieve.
// Where as in the calculation step we are dividing the number every time by 
// the smallest prime number till it becomes 1.
// So, let’s consider a worst case in which every time the SPF is 2 .
// Therefore will have log n division steps.


// Hence, We can say that our Time Complexity will be O(log n) in worst case.


    static ArrayList<Integer> getPrimeFactorization(int x) 
    { 
        ArrayList<Integer> ret = new ArrayList<Integer>(); 
        while (x != 1) 
        { 
            ret.add(spf[x]); 
            x = x / spf[x]; 
        } 
        return ret; 
    } 
       
 //////////////////////////////////////////////////////////////////////////////////////////////////
 //////////////////////////////////////////////////////////////////////////////////////////////////
   
public static void merge(int arr[], int l, int m, int r)
    {
        // Find sizes of two subarrays to be merged
        int n1 = m - l + 1;
        int n2 = r - m;
 
        /* Create temp arrays */
        int L[] = new int[n1];
        int R[] = new int[n2];
 
       //Copy data to temp arrays
        for (int i=0; i<n1; ++i)
            L[i] = arr[l + i];
        for (int j=0; j<n2; ++j)
            R[j] = arr[m + 1+ j];
 
 
        /* Merge the temp arrays */
 
        // Initial indexes of first and second subarrays
        int i = 0, j = 0;
 
        // Initial index of merged subarry array
        int k = l;
        while (i < n1 && j < n2)
        {
            if (L[i] <= R[j])
            {
                arr[k] = L[i];
                i++;
            }
            else
            {
                arr[k] = R[j];
                j++;
            }
            k++;
        }
 
        /* Copy remaining elements of L[] if any */
        while (i < n1)
        {
            arr[k] = L[i];
            i++;
            k++;
        }
 
        /* Copy remaining elements of R[] if any */
        while (j < n2)
        {
            arr[k] = R[j];
            j++;
            k++;
        }
    }
 
    // Main function that sorts arr[l..r] using
    // merge()
  public static void sort(int arr[], int l, int r)
    {
        if (l < r)
        {
            // Find the middle point
            int m = (l+r)/2;
 
            // Sort first and second halves
            sort(arr, l, m);
            sort(arr , m+1, r);
 
            // Merge the sorted halves
            merge(arr, l, m, r);
        }
    }

public static void sort(long arr[], int l, int r)
    {
        if (l < r)
        {
            // Find the middle point
            int m = (l+r)/2;
 
            // Sort first and second halves
            sort(arr, l, m);
            sort(arr , m+1, r);
 
            // Merge the sorted halves
            merge(arr, l, m, r);
        }
    }


public static void merge(long arr[], int l, int m, int r)
    {
        // Find sizes of two subarrays to be merged
        int n1 = m - l + 1;
        int n2 = r - m;
 
        /* Create temp arrays */
        long L[] = new long[n1];
        long R[] = new long[n2];
 
        //Copy data to temp arrays
        for (int i=0; i<n1; ++i)
            L[i] = arr[l + i];
        for (int j=0; j<n2; ++j)
            R[j] = arr[m + 1+ j];
 
 
        /* Merge the temp arrays */
 
        // Initial indexes of first and second subarrays
        int i = 0, j = 0;
 
        // Initial index of merged subarry array
        int k = l;
        while (i < n1 && j < n2)
        {
            if (L[i] <= R[j])
            {
                arr[k] = L[i];
                i++;
            }
            else
            {
                arr[k] = R[j];
                j++;
            }
            k++;
        }
 
        /* Copy remaining elements of L[] if any */
        while (i < n1)
        {
            arr[k] = L[i];
            i++;
            k++;
        }
 
        /* Copy remaining elements of R[] if any */
        while (j < n2)
        {
            arr[k] = R[j];
            j++;
            k++;
        }
    }
 

 /////////////////////////////////////////////////////////////////////////////////////////
 
	public static long knapsack(int[] weight,long value[],int maxWeight){

        
        int n=  value.length ;
        
	
	//dp[i] stores the profit with KnapSack capacity "i" 
  long []dp = new long[maxWeight+1]; 
      
    //initially profit with 0 to W KnapSack capacity is 0 
    Arrays.fill(dp, 0); 
  
    // iterate through all items 
    for(int i=0; i < n; i++)  
      
        //traverse dp array from right to left 
        for(int j = maxWeight; j >= weight[i]; j--) 
            dp[j] = Math.max(dp[j] , value[i] + dp[j - weight[i]]); 
              
    /*above line finds out maximum of dp[j](excluding ith element value) 
    and val[i] + dp[j-wt[i]] (including ith element value and the 
    profit with "KnapSack capacity - ith element weight") */
    return dp[maxWeight]; 
	}

///////////////////////////////////////////////////////////////////////////////////////////
//////////////////////////////////////////////////////////////////////////////////////////


// to return max sum of any subarray in given array
public static long kadanesAlgorithm(long[] arr)
{
    
    if(arr.length == 0)return  0 ;
    
      long[] dp = new long[arr.length] ;
      
      dp[0] = arr[0] ;
      long max =  dp[0] ;
      
      
      for(int i = 1; i <  arr.length ; i++)
      {
            if(dp[i-1] > 0)
            {
                  dp[i] = dp[i-1] + arr[i] ;
            }
            else{
                  dp[i] = arr[i] ;
            }
            
            if(dp[i] >  max)max = dp[i] ;
            
      }
      
      return max  ;
      
}
/////////////////////////////////////////////////////////////////////////////////////////////
public static long kadanesAlgorithm(int[] arr)
{
     if(arr.length == 0)return  0 ;
    
      long[] dp = new long[arr.length] ;
      
      dp[0] = arr[0] ;
      long max =  dp[0] ;
      
      
      for(int i = 1; i <  arr.length ; i++)
      {
            if(dp[i-1] > 0)
            {
                  dp[i] = dp[i-1] + arr[i] ;
            }
            else{
                  dp[i] = arr[i] ;
            }
            
            if(dp[i] >  max)max = dp[i] ;
            
      }
      
      return max  ;
      
}

      
///////////////////////////////////////////////////////////////////////////////////////



/////////////////////////////////////////////////////////////////////////////////////////

public static long binarySerachGreater(int[] arr , int start , int end , int val)
{
      
      // fing total no of elements strictly grater than val in sorted array arr 
      
      
      if(start >  end)return  0 ; //Base case
      
      
      int mid = (start + end)/2  ;
      
      if(arr[mid] <=val)
      {
          return binarySerachGreater(arr,mid+1, end ,val) ; 
            
      }
      else{
            
         return binarySerachGreater(arr,start , mid -1,val) + end-mid+1 ;    
            
      }
      
      
}

//////////////////////////////////////////////////////////////////////////////////
////////////////////////////////////////////////////////////////////////////////////

//TO GENERATE ALL(DUPLICATE ALSO EXIST) PERMUTATIONS OF A STRING


// JUST CALL generatePermutation( str,  start,  end) start :inclusive ,end : exclusive 

//Function for swapping the characters at position I with character at position j  
    public static String swapString(String a, int i, int j) {  
        char[] b =a.toCharArray();  
        char ch;  
        ch = b[i];  
        b[i] = b[j];  
        b[j] = ch;  
        return String.valueOf(b);  
    }  
      
//Function for generating different permutations of the string  
    public static void generatePermutation(String str, int start, int end)  
    {  
        //Prints the permutations  
        if (start == end-1)  
            System.out.println(str);  
        else  
        {  
            for (int i = start; i < end; i++)  
            {  
                //Swapping the string by fixing a character  
                str = swapString(str,start,i);  
                //Recursively calling function generatePermutation() for rest of the characters   
                generatePermutation(str,start+1,end);  
                //Backtracking and swapping the characters again.  
                str = swapString(str,start,i);  
            }  
        }  
    }  



////////////////////////////////////////////////////////////////////////////////////////////////////
//////////////////////////////////////////////////////////////////////////////////////////////////////

public static long factMod(long n, long mod) {
    if (n <= 1) return 1;
    long ans = 1;
    for (int i = 1; i <= n; i++) {
      ans = (ans * i) % mod;
    }
    return ans;
  }


/////////////////////////////////////////////////////////////////////////////////////////////
//////////////////////////////////////////////////////////////////////////////////////////////////

public static long power(int a  ,int b)
    {
        //time comp : o(logn) 
        
        long x = (long)(a) ;
         long n = (long)(b) ;
        
        if(n==0)return 1 ;
        if(n==1)return x;
        
        long ans =1L  ;
       
      while(n>0)
      {
          if(n % 2 ==1)
          {
              ans = ans *x ;
          }
           
          n = n/2L ;
           
          x =  x*x ;
           
      }
       
      return ans ;
    }
    
    public static long power(long a  ,long b)
    {
        //time comp : o(logn) 
        
        long x = (a) ;
         long n = (b) ;
        
        if(n==0)return 1L ;
        if(n==1)return x;
        
        long ans =1L  ;
       
      while(n>0)
      {
          if(n % 2 ==1)
          {
              ans = ans *x ;
          }
           
          n = n/2L ;
           
          x =  x*x ;
           
      }
       
      return ans ;
    }

    
    
    

////////////////////////////////////////////////////////////////////////////////////////////////////
public static long powerMod(long x, long n, long mod) {
    //time comp : o(logn)
    
    if(n==0)return 1L ;
        if(n==1)return x;
        
    
    long ans = 1;
    while (n > 0) {
      if (n % 2 == 1) ans = (ans * x) % mod;
      x = (x * x) % mod;
      n /= 2;
    }
    return ans;
  }
 
//////////////////////////////////////////////////////////////////////////////////

/////////////////////////////////////////////////////////////////////////////////

/*
lowerBound - finds largest element equal or less than value paased
upperBound - finds smallest element equal or more than value passed

if not present return -1;

*/

public static long lowerBound(long[] arr,long k)
	{
		long ans=-1;
		
		int start=0;
		int end=arr.length-1;
		
		while(start<=end)
		{
			int mid=(start+end)/2;
			
			if(arr[mid]<=k)
			{
				ans=arr[mid];
				start=mid+1;
			}
			else
			{
				end=mid-1;
			}
			
		}
		
		return ans;
		
	}
	
	public static int lowerBound(int[] arr,int k)
	{
		int ans=-1;
		
		int start=0;
		int end=arr.length-1;
		
		while(start<=end)
		{
			int mid=(start+end)/2;
			
			if(arr[mid]<=k)
			{
				ans=arr[mid];
				start=mid+1;
			}
			else
			{
				end=mid-1;
			}
			
		}
		
		return ans;
		
	}
	
	
	public static long upperBound(long[] arr,long k)
	{
		long ans=-1;
		
		int start=0;
		int end=arr.length-1;
		
		while(start<=end)
		{
			int mid=(start+end)/2;
			
			if(arr[mid]>=k)
			{
				ans=arr[mid];
				end=mid-1;
			}
			else
			{
				start=mid+1;
			}
			
		}
		
		return ans;
	}
	
	
	public static int upperBound(int[] arr,int k)
	{
		int ans=-1;
		
		int start=0;
		int end=arr.length-1;
		
		while(start<=end)
		{
			int mid=(start+end)/2;
			
			if(arr[mid]>=k)
			{
				ans=arr[mid];
				end=mid-1;
			}
			else
			{
				start=mid+1;
			}
			
		}
		
		return ans;
	}
	

//////////////////////////////////////////////////////////////////////////////////////////

public static void printArray(int[] arr , int si ,int ei)
{
    for(int i = si  ; i  <= ei ; i++)
    {
        out.print(arr[i] +" ") ;
    }
    
}

public static void printArrayln(int[] arr , int si ,int ei)
{
    for(int i = si  ; i  <= ei ; i++)
    {
        out.print(arr[i] +" ") ;
    }
    out.println() ;
}


public static void printLArray(long[] arr , int si , int ei)
{
    for(int i = si ; i  <= ei ; i++)
    {
        out.print(arr[i] +" ") ;
    }
   
}




public static void printLArrayln(long[] arr , int si , int ei)
{
    for(int i = si ; i  <= ei ; i++)
    {
        out.print(arr[i] +" ") ;
    }
    out.println() ;
   
}

public static void printtwodArray(int[][] ans)
{
    for(int i = 0; i< ans.length ; i++)
    {
        for(int j  = 0 ; j <  ans[0].length ; j++)out.print(ans[i][j] +" ");
        out.println() ;
    }
    out.println() ;
   
}

  
   static long modPow(long a, long x, long p) {
    //calculates a^x mod p in logarithmic time.
    long res = 1;
    while(x > 0) {
        if( x % 2 != 0) {
            res = (res * a) % p;
        }
        a = (a * a) % p;
        x /= 2;
    }
    return res;
}
 
 
 
  static long modInverse(long a, long p) {
    //calculates the modular multiplicative of a mod p.
    //(assuming p is prime).
    return modPow(a, p-2, p);
}
 
 
 
static long modBinomial(long n, long k, long p) {
// calculates C(n,k) mod p (assuming p is prime).
 
    long numerator = 1; // n * (n-1) * ... * (n-k+1)
    for (int i=0; i<k; i++) {
        numerator = (numerator * (n-i) ) % p;
    }
 
    long denominator = 1; // k!
    for (int i=1; i<=k; i++) {
        denominator = (denominator * i) % p;
    }
 
    // numerator / denominator mod p.
    return ( numerator* modInverse(denominator,p) ) % p;
}
 
 
 static void update(int val , long[] bit ,int n)
 {
     for( ; val <= n ; val += (val &(-val)) )
     {
         bit[val]++ ;
     }
    
     
 }
 
 
 static long query(int val , long[] bit , int n)
 {
     long ans = 0L; 
     for( ; val >=1 ; val-=(val&(-val))  )ans += bit[val];
     
     return ans ;
 }



static int countSetBits(long n) 
    { 
        int count = 0; 
        while (n > 0) { 
            n = (n) & (n - 1L); 
            count++; 
        } 
        return count; 
    } 


static int abs(int x)
{
    if(x < 0)x = -1*x ;
    
    return x ;
}


static long abs(long x)
{
    if(x < 0)x = -1L*x ;
    
    return x ;
}



/////////////////////////////////////////////////////////////////////////////////////
////////////////////////////////////////////////////////////////////////////////////////////
////////////////////////////////////////////////////////////////////////////////////////////

// static ArrayList<Integer>[] tree ;
// static long[] child;
// static int mod= 1000000007 ;
// static int[][] pre  = new int[3001][3001];
// static int[][] suf = new int[3001][3001] ;

//program to calculate noof nodes in subtree for every vertex including itself 

// static void dfs(int sv)
// {
//     child[sv] = 1L; 
    
    
//     for(Integer x : tree[sv])
//     {
//         if(child[x] == 0)
//         {
          
//           dfs(x) ;
          
//           child[sv] += child[x] ;
//         }
//     }
// }

 
static int bs(long[] arr , long key , int n, int s , int e)
{
    int ans = 0 ;
  
   while( s <= e)
   {
       int m = (s+e)/2 ;
       
       if(arr[m] <= key)
       {
           ans =m ;
           s=m+1 ;
           
       }
       
       else{
           
          e=m-1  ; 
           
       }
       
   }
    return ans  ;
    
    
    
}




//////////////////////////////////////////////////////////////////////////////////////////////
//////////////////////////////////////////////////////////////////////////////////////////
////////////////////////////////////////////////////////////////////////////////////////////

public static void solve()
{
FastReader scn = new FastReader() ;

//Scanner scn = new Scanner(System.in);
//int[] store = {2 ,3, 5 , 7  ,11 , 13 , 17 , 19 , 23 , 29 , 31 , 37 } ;

// product of first 11 prime nos is greater than 10 ^ 12;
//sieve() ;
//ArrayList<Integer> arr[] = new ArrayList[n] ;
ArrayList<Integer> list = new ArrayList<>() ;
ArrayList<Long> lista = new ArrayList<>() ;
ArrayList<Long> listb = new ArrayList<>() ;
// ArrayList<Integer> lista = new ArrayList<>() ;
// ArrayList<Integer> listb = new ArrayList<>() ;
//ArrayList<String> lists = new ArrayList<>() ;

HashMap<Integer,Integer> map = new HashMap<>() ;
//HashMap<Long,Long> map = new HashMap<>() ;
HashMap<Integer,Integer> mapx  = new HashMap<>() ;
HashMap<Integer,Integer> mapy  = new HashMap<>() ;
//HashMap<String,Integer> maps = new HashMap<>() ;
//HashMap<Integer,Boolean> mapb = new HashMap<>() ;
//HashMap<Point,Integer> point = new HashMap<>() ; 

 Set<Integer> set = new HashSet<>() ;
 Set<Integer> setx = new HashSet<>() ;
 Set<Integer> sety = new HashSet<>() ;

StringBuilder sb =new StringBuilder("") ;

//Collections.sort(list);

//if(map.containsKey(arr[i]))map.put(arr[i] , map.get(arr[i]) +1 ) ;
//else map.put(arr[i],1) ;

// if(map.containsKey(temp))map.put(temp , map.get(temp) +1 ) ;
// else map.put(temp,1) ;

//int bit  =Integer.bitCount(n);
// gives total no of set bits in n;

// Arrays.sort(arr, new Comparator<Pair>() {
// 			@Override
// 			public int compare(Pair a, Pair b) {
// 				if (a.first != b.first) {
// 					return a.first - b.first; // for increasing order of first
// 				}
// 				return a.second - b.second ; //if first is same then sort on second basis
// 			}
// 		});



int testcase = 1;
 //testcase = scn.nextInt() ;
for(int testcases =1  ; testcases <= testcase ;testcases++)
{
    
 //if(map.containsKey(arr[i]))map.put(arr[i],map.get(arr[i])+1) ;else map.put(arr[i],1) ;
 //if(map.containsKey(temp))map.put(temp,map.get(temp)+1) ;else map.put(temp,1) ;
// tree = new ArrayList[n] ;
// child  = new long[n] ;
// for(int i = 0; i< n; i++)
// {
//     tree[i] = new ArrayList<Integer>();
//



int n = scn.nextInt() ;
int xor = 0 ;

int[] arr = new int[n+1];
for(int i = 1; i<=n ;i++){arr[i] = scn.nextInt() ;  xor = xor ^ arr[i] ; }

if((n & 1) == 0 && xor != 0)out.println("NO") ;

else{
    out.println("YES") ;
    
    if( n % 2 == 0)n=n-1 ;
    
    out.println(n-2) ;
    
    
    int pr= 1 ;
    
    
    while(pr <=n-2  ){
        
        out.println(pr+" " + (pr+1) +" " + (pr+2) ) ;
        pr = pr+2  ;
    }
    
   // out.println("@") ;
    
    pr = 1 ;
    
    
    while(pr <=n-4  ){
        
        out.println(pr+" " + (pr+1) +" " + (n) ) ;
        pr = pr+2  ;
    }
    
    
    
    
}


 //out.println("@") ;
set.clear() ;
sb.delete(0 , sb.length()) ;
list.clear() ;lista.clear() ;listb.clear() ;
map.clear() ;
mapx.clear() ;
mapy.clear() ;
setx.clear() ;sety.clear() ;

} // test case  end loop


out.flush() ;  
} // solve fn ends


public static void main (String[] args) throws java.lang.Exception
{
  

solve() ;
      
}


}
  
 class Pair 
{
  long first ;
  
 long second  ;
  
  
 
    
      
@Override
	public String toString() {
	
	String ans = "" ;
	ans  += this.first ;
	ans += " ";
	ans += this.second ;
	
	return ans  ;
	}


}