http://codeforces.net/contest/272/problem/D

can somebody point out mistake in my code getting WA for case 2 1 2 2 2 4

#include <bits/stdc++.h>
#define ull unsigned long long
#define ll long long
#define pii pair<int,int>
#define pb(x) push_back(x)
#define S(x) scanf("%d",&x)
#define Sl(x) scanf("%lld",&x)
#define M(x,i) memset(x,i,sizeof(x))
#define F(i,a,n) for(i=(a);i<(n);++i)
#define FD(i,a,n) for(i=(a);i>=(n);--i)
using namespace std;
map<int,int> mp;
int a[100005];
int b[100005];
ll fact[200005];
int MOD=1;
ll modm(ll a,ll b)
{
	return (a*b)%MOD;
}
void pre()
{
	int i;
	fact[0]=1;
	F(i,1,200005){
		fact[i]=modm(fact[i-1],(ll)i);
	}
}
int fi(int n) 
{ 
	int result = n; 
	for(int i=2;i*i <= n;i++) 
	{ 
		if (n % i == 0) result -= result / i; 
		while (n % i == 0) n /= i; 
	} 
	if (n > 1) result -= result / n; 
	return result; 
} 
unsigned long long modPow(unsigned long long x,unsigned long long y)
{
	unsigned long long r=1, a=x;
	while (y > 0) {
		if ( (y&1)==1 ) {
			r = (r * a) % MOD;
		}
		a = (a * a) % MOD;
		y /= 2;
	}

	return r;
}
// Modular multiplicative inverse through Fermat's little theorem:
unsigned long long modInverse(long x,int y)
{
	return modPow(x, y-1);
}
int main()
{
	int n,i,cnt=0;
	ll ans1,ans2;
	S(n);
	F(i,0,n){
		S(a[i]);
		mp[a[i]]++;
	}
	F(i,0,n){
		S(b[i]);
		mp[b[i]]++;
	}

	S(MOD);
	pre();

	F(i,0,n){
		if(a[i]==b[i]){
			cnt++;
		}
	}

	ans1=modPow(2,cnt);
	ans2=1;
	map<int,int> ::iterator it;
	for(it=mp.begin();it!=mp.end();it++){
		//cout<<(*it).first<<" "<<(*it).second<<" "<<fact[(*it).second]<<endl;
		ans2=modm(ans2,fact[(*it).second]);
	}

	if(ans1==0)ans1=1;
        if(ans2==0)ans2=1;
	cout<<modm(ans2,modInverse(ans1,fi(MOD)))<<endl;