Problem: There are n coins labeled from 1 to n. Initially, coin c_i is on position i and is facing upwards ((c_1, c_2, ..., c_n) is a permutation of numbers from 1 to n). You can do some operations on these coins. 

In one operation, you can do the following:

  * Choose 2 distinct indices i and j.

  * Then, swap the coins on positions i and j.

  * Then, flip both coins on positions i and j. (If they are initially faced up, they will be faced down after the operation and vice versa)




Construct a sequence of at most n+1 operations such that after performing all these operations the coin i will be on position i at the end, facing up.

Note that you do not need to minimize the number of operations.

Input

The first line contains an integer n (3 ≤ n ≤ 2 ⋅ 10^5) — the number of coins.

The second line contains n integers c_1,c_2,...,c_n (1 ≤ c_i ≤ n, c_i ≠ c_j for i≠ j).

Output

In the first line, output an integer q (0 ≤ q ≤ n+1) — the number of operations you used.

In the following q lines, output two integers i and j (1 ≤ i, j ≤ n, i ≠ j) — the positions you chose for the current operation.

Examples

Input


3
2 1 3


Output


3
1 3
3 2
3 1


Input


5
1 2 3 4 5


Output


0

Note

Let coin i facing upwards be denoted as i and coin i facing downwards be denoted as -i.

The series of moves performed in the first sample changes the coins as such:

  * [~~~2,~~~1,~~~3] 
  * [-3,~~~1,-2] 
  * [-3,~~~2,-1] 
  * [~~~1,~~~2,~~~3] 



In the second sample, the coins are already in their correct positions so there is no need to swap.

Solution (in CPP):

Solution:
//Original Code:
//#include <self/utility>
//#include <self/debug>
//using namespace std;
//int n;
//int a[200005];
//vector<pii> res;
//
//void push(int x,int y)
//{
//	res.push_back(mp(x,y));
//}
//
//void print()
//{
//	cout<<res.size()<<endl;
//	for(auto [x,y]:res)
//	{
//		printf("%d %d\n",x+1,y+1);
//	}
//}
//
//int visit[200005];
//vector<vector<int> > cycles;
//
//void process(vector<int> v)
//{
//	if(v.size()==2)
//	{
//		int x=v[0],y=v[1];
//		int z;
//		if(x!=0 && y!=0) z=0;
//		if(x!=1 && y!=1) z=1;
//		if(x!=2 && y!=2) z=2;
//		push(x,z);
//		push(y,z);
//		push(x,z);
//		return;
//	}
//	for(int i=2;i<v.size();i++)
//	{
//		push(v[1],v[i]);
//	}
//	push(v[0],v[2]);
//	push(v[0],v[1]);
//	push(v[1],v[2]);
//}
//
//void solve(vector<int> v)
//{
//	for(int i=1;i<v.size();i++)
//	{
//		push(v[0],v[i]);
//	}
//}
//
//int main()
//{
//	// freopen("input.txt","r",stdin);
//	cin>>n;
//	for(int i=0;i<n;i++)
//	{
//		scanf("%d",a+i);
//		a[i]--;
//	}
//	for(int i=0;i<n;i++)
//	{
//		if(visit[i]) continue;
//		int now=a[i];
//		vector<int> v;
//		while(now!=i)
//		{
//			v.push_back(now);
//			visit[now]=true;
//			now=a[now];
//		}
//		v.push_back(now);
//		visit[now]=true;
//		if(v.size()==1) continue;
//		cycles.push_back(v);
//	}
//	if(cycles.size()&1)
//	{
//		process(cycles.back());
//		cycles.pop_back();
//	}
//	for(int i=0;i<cycles.size();i+=2)
//	{
//		push(cycles[i][0],cycles[i+1][0]);
//		swap(cycles[i][0],cycles[i+1][0]);
//		solve(cycles[i]);
//		solve(cycles[i+1]);
//		push(cycles[i][0],cycles[i+1][0]);
//	}
//	print();
//	return 0;
//}

//substituted with C++ Inliner
#ifndef _SELF_UTILITY
#define _SELF_UTILITY 1
#include <numeric>
#include <iostream>
#include <algorithm>
#include <cmath>
#include <stdio.h>
#include <stdlib.h>
#include <vector>
#include <map>
#include <queue>
#include <set>
#include <string>
#include <string.h>
#include <stack>
#include <assert.h>
#include <bitset>
#include <time.h>
#define Endl endl
#define mp make_pair
#define mt make_tuple
#define ll long long 
#define ull unsigned long long
#define pii pair<int,int>
#define over(A) {cout<<A<<endl;exit(0);}
#define all(A) A.begin(),A.end()
#define quickcin ios_base::sync_with_stdio(false);
#ifdef __TAKE_MOD
int mod;
#else
#ifdef __TAKE_CONST_MOD
const int mod=__TAKE_CONST_MOD;
#else
const int mod=1000000007;
#endif
#endif
const int gmod=3;
const int inf=1039074182;
const double eps=1e-9;
const ll llinf=2LL*inf*inf;
template <typename T1,typename T2> inline void chmin(T1 &x,T2 b) {if(b<x) x=b;}
template <typename T1,typename T2> inline void chmax(T1 &x,T2 b) {if(b>x) x=b;}
inline void chadd(int &x,int b) {x+=b-mod;x+=(x>>31 & mod);}
template <typename T1,typename T2> inline void chadd(T1 &x,T2 b) {x+=b;if(x>=mod) x-=mod;}
template <typename T1,typename T2> inline void chmul(T1 &x,T2 b) {x=1LL*x*b%mod;}
template <typename T1,typename T2> inline void chmod(T1 &x,T2 b) {x%=b,x+=b;if(x>=b) x-=b;}
template <typename T> inline T mabs(T x) {return (x<0?-x:x);}
using namespace std;
#endif
#ifndef _SELF_DEBUG
#define _SELF_DEBUG 1
#ifndef _SELF_OPERATOR
#define _SELF_OPERATOR 1
using namespace std;
template <typename T>
ostream &operator<<(ostream &cout, vector<T> vec)
{
	cout << "{";
	for (int i = 0; i < (int)vec.size(); i++)
	{
		cout << vec[i];
		if (i != (int)vec.size() - 1)
			cout << ',';
	}
	cout << "}";
	return cout;
}

template <typename T1, typename T2>
ostream &operator<<(ostream &cout, pair<T1, T2> p)
{
	cout << "(" << p.first << ',' << p.second << ")";
	return cout;
}

template <typename T, typename T2>
ostream &operator<<(ostream &cout, set<T, T2> s)
{
	vector<T> t;
	for (auto x : s)
		t.push_back(x);
	cout << t;
	return cout;
}

template <typename T, typename T2>
ostream &operator<<(ostream &cout, multiset<T, T2> s)
{
	vector<T> t;
	for (auto x : s)
		t.push_back(x);
	cout << t;
	return cout;
}

template <typename T>
ostream &operator<<(ostream &cout, queue<T> q)
{
	vector<T> t;
	while (q.size())
	{
		t.push_back(q.front());
		q.pop();
	}
	cout << t;
	return cout;
}

template <typename T1, typename T2, typename T3>
ostream &operator<<(ostream &cout, map<T1, T2, T3> m)
{
	for (auto &x : m)
	{
		cout << "Key: " << x.first << ' ' << "Value: " << x.second << endl;
	}
	return cout;
}

template <typename T1, typename T2>
void operator+=(pair<T1, T2> &x,const pair<T1, T2> y)
{
	x.first += y.first;
	x.second += y.second;
}
template <typename T1,typename T2>
pair<T1,T2> operator + (const pair<T1,T2> &x,const pair<T1,T2> &y)
{
	return make_pair(x.first+y.first,x.second+y.second);
}

template <typename T1,typename T2>
pair<T1,T2> operator - (const pair<T1,T2> &x,const pair<T1,T2> &y)
{
	return mp(x.first-y.first,x.second-y.second);
}

template <typename T1, typename T2>
pair<T1, T2> operator-(pair<T1, T2> x)
{
	return make_pair(-x.first, -x.second);
}

template <typename T>
vector<vector<T>> operator~(vector<vector<T>> vec)
{
	vector<vector<T>> v;
	int n = vec.size(), m = vec[0].size();
	v.resize(m);
	for (int i = 0; i < m; i++)
	{
		v[i].resize(n);
	}
	for (int i = 0; i < m; i++)
	{
		for (int j = 0; j < n; j++)
		{
			v[i][j] = vec[j][i];
		}
	}
	return v;
}
#endif
#include <sstream>
void print0x(int x)
{
	std::vector <int> vec;
	while(x)
	{
		vec.push_back(x&1);
		x>>=1;
	}
	std::reverse(vec.begin(),vec.end());
	for(int i=0;i<(int)vec.size();i++)
	{
		std::cout<<vec[i];
	}
	std::cout<<' ';
}

template <typename T>
void print0x(T x,int len)
{
	std::vector <int> vec;
	while(x)
	{
		vec.push_back(x&1);
		x>>=1;
	}
	reverse(vec.begin(),vec.end());
	for(int i=(int)vec.size();i<len;i++)
	{
		putchar('0');
	}
	for(size_t i=0;i<vec.size();i++)
	{
		std::cout<<vec[i];
	}
	std::cout<<' ';
}
vector<string> vec_splitter(string s) {
	s += ',';
	vector<string> res;
	while(!s.empty()) {
		res.push_back(s.substr(0, s.find(',')));
		s = s.substr(s.find(',') + 1);
	}
	return res;
}
void debug_out(
vector<string> __attribute__ ((unused)) args,
__attribute__ ((unused)) int idx, 
__attribute__ ((unused)) int LINE_NUM) { cerr << endl; } 
template <typename Head, typename... Tail>
void debug_out(vector<string> args, int idx, int LINE_NUM, Head H, Tail... T) {
	if(idx > 0) cerr << ", "; else cerr << "Line(" << LINE_NUM << ") ";
	stringstream ss; ss << H;
	cerr << args[idx] << " = " << ss.str();
	debug_out(args, idx + 1, LINE_NUM, T...);
}
#define debug(...) debug_out(vec_splitter(#__VA_ARGS__), 0, __LINE__, __VA_ARGS__)
#endif
using namespace std;
int n;
int a[200005];
vector<pii> res;

void push(int x,int y)
{
	res.push_back(mp(x,y));
}

void print()
{
	cout<<res.size()<<endl;
	for(auto [x,y]:res)
	{
		printf("%d %d\n",x+1,y+1);
	}
}

int visit[200005];
vector<vector<int> > cycles;

void process(vector<int> v)
{
	if(v.size()==2)
	{
		int x=v[0],y=v[1];
		int z;
		if(x!=0 && y!=0) z=0;
		if(x!=1 && y!=1) z=1;
		if(x!=2 && y!=2) z=2;
		push(x,z);
		push(y,z);
		push(x,z);
		return;
	}
	for(int i=2;i<v.size();i++)
	{
		push(v[1],v[i]);
	}
	push(v[0],v[2]);
	push(v[0],v[1]);
	push(v[1],v[2]);
}

void solve(vector<int> v)
{
	for(int i=1;i<v.size();i++)
	{
		push(v[0],v[i]);
	}
}

int main()
{
//	// freopen("input.txt","r",stdin);
	cin>>n;
	for(int i=0;i<n;i++)
	{
		scanf("%d",a+i);
		a[i]--;
	}
	for(int i=0;i<n;i++)
	{
		if(visit[i]) continue;
		int now=a[i];
		vector<int> v;
		while(now!=i)
		{
			v.push_back(now);
			visit[now]=true;
			now=a[now];
		}
		v.push_back(now);
		visit[now]=true;
		if(v.size()==1) continue;
		cycles.push_back(v);
	}
	if(cycles.size()&1)
	{
		process(cycles.back());
		cycles.pop_back();
	}
	for(int i=0;i<cycles.size();i+=2)
	{
		push(cycles[i][0],cycles[i+1][0]);
		swap(cycles[i][0],cycles[i+1][0]);
		solve(cycles[i]);
		solve(cycles[i+1]);
		push(cycles[i][0],cycles[i+1][0]);
	}
	print();
	return 0;
}