#include <cstdlib>
#include <cmath>
#include <climits>
#include <cfloat>
#include <map>
//#include <utility>
#include <set>
#include <iostream>
//#include <memory>
#include <string>
#include <vector>
#include <algorithm>
//#include <functional>
#include <sstream>
//#include <deque>
#include <complex>
#include <stack>
#include <queue>
#include <cstdio>
//#include <cctype>
#include <cstring>
//#include <ctime>
#include <iterator>
#include <bitset>
//#include <numeric>
//#include <list>
//#include <iomanip>

#if __cplusplus >= 201103L
#include <array>
#include <tuple>
#include <initializer_list>
#include <unordered_set>
#include <unordered_map>
#include <forward_list>

#define cauto const auto&
#else

#endif

using namespace std;


namespace{
typedef long long ll;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;

typedef vector<int> vint;
typedef vector<vector<int> > vvint;
typedef vector<long long> vll, vLL;
typedef vector<vector<long long> > vvll, vvLL;

#define VV(T) vector<vector< T > >

template <class T>
void initvv(vector<vector<T> > &v, int a, int b, const T &t = T()){
    v.assign(a, vector<T>(b, t));
}

template <class F, class T>
void convert(const F &f, T &t){
    stringstream ss;
    ss << f;
    ss >> t;
}


#define reep(i,a,b) for(int i=(a);i<(b);++i)
#define rep(i,n) reep((i),0,(n))
#define ALL(v) (v).begin(),(v).end()
#define PB push_back
#define F first
#define S second
#define mkp make_pair
#define RALL(v) (v).rbegin(),(v).rend()


#define MOD 1000000007LL
#define EPS 1e-8
static const int INF=1<<24;

vint used;
	// vint a(n);
vint a;
int n;
int foo(int x){
	if(used[x]){
		// bool f=false;
		rep(i,n){
			if(used[i]==0){
				return 0;
			}
		}
		return 1;
	}
	used[x]=1;
	int ret=foo(a[x]);
	used[x]=0;
	return ret;
}

void mainmain(){
	// int n;
	cin>>n;
	a=vint(n);
	used=vint(n,0);
	rep(i,n){
		cin>>a[i];
		a[i]--;
	}
	int cnt=0;
	rep(i,n){
		if(i!=a[i]&&a[i]==a[a[a[i]]]){
			cnt++;
			// cout<<"No\n";
			// return;
		}
	}
	cout<<cnt<<endl;
	if(cnt==2){
		cout<<"No\n";
		return;
	}
	cout<<"Yes\n";
	return;
	int t;
	rep(i,n){
		if(a[i]==i){
			used[i]=1;
		}
		else t=i;
	}
	bool f=true;
	rep(i,n) if(used[i]==0) f=false;
	if(f){
		cout<<"Yes\n";
		return;
	}
	rep(i,n){
		if(foo(i)){
			cout<<"Yes\n";
			return;
		}
	}
	cout<<"No\n";
}



}
main() try{
    mainmain();
}
catch(...){
}