最后一个捆绑测试里面有几个点WA了。我的思路好像不太一样，我是用错位排序来推的。求 hack 数据。玄关

// Author: chenly8128
// Created: 2025-01-11 17:22:28

#include <bits/stdc++.h>
#define int long long
using namespace std;
inline int read(void) {
	int res = 0;bool flag = true;char c = getchar();
	while (c < '0' || c > '9') {flag ^= (c == '-');c = getchar();}
	while (c >= '0' && c <= '9') {res = (res << 3) + (res << 1) + (c ^ 48);c = getchar();}
	return flag ? res : -res;
}
const int MAXN = 1e6+10;
const int mod = 998244353;
int n,p[MAXN],d[MAXN];
int cnt[MAXN],ghi[MAXN],inv[MAXN];
bool vis[MAXN],b;
vector <int> g[MAXN];
void dfs (int x,int col) {
	vis[x] = true;
	sort (g[x].begin(),g[x].end());
	int sz = unique (g[x].begin(),g[x].end()) - g[x].begin();
	cnt[col]++;
	if (sz >= 3) {
		puts ("0");
		exit(0);
	}
	if (sz <= 1) b = true;
	for (int v : g[x]) {
		if (sz > 1 && v == x) {
			puts ("0");
			exit(0);
		}
		if (!vis[v]) dfs (v,col);
	}
}
int power_mod (int x,int k) {
	int ans = 1;
	while (k) {
		if (k&1) ans = ans * x % mod;
		x = x * x % mod;
		k >>= 1;
	}
	return ans;
}
int C (int a,int b) {
	return ghi[a] * inv[b] % mod * inv[a-b] % mod;
}
signed main (void) {
	n = read();
	for (int i = 1;i <= n;i++) {
		p[i] = read();
		g[p[i]].push_back(i);
		g[i].push_back(p[i]);
	}
	int now = 0,k = 0,now2 = 0,m = 0;
	int ans = 1;
	for (int i = 1;i <= n;i++)
		if (!vis[i]) {
			b = false;
			dfs (i,++now);
			if (cnt[now] > 2) {
				now2++;
				if (b) m++;
			}
			else if (cnt[now] == 2) k++;
		}
	ans = power_mod(2,now2);
	ghi[0] = inv[0] = 1;
	for (int i = 1;i <= n;i++) {
		ghi[i] = ghi[i-1] * i % mod;
		inv[i] = power_mod(ghi[i],mod-2);
	}
	d[0] = ghi[m];
	for (int i = 1;i <= k;i++)
		d[i] = (m+i-1) * (d[i-1] + (i >= 2 ? d[i-2] : 0)) % mod;
	int tot = 0;
	for (int i = 0;i <= k;i++)
		tot = (tot + power_mod(2,k-i) * d[k-i] % mod * C(k,i)) % mod;
	printf ("%lld\n",ans * tot % mod);
	return 0;
}