#include<bits/stdc++.h>
using namespace std;
using ll = long long;
//using LL = __int128
#define N 400010
#define mod 1000000007ll
ll n, a[N], bu[N], ans[N], fac[N] = {1}, inv[N], sum[N], p[N] = {1};
ll bigmul(ll a, ll b, ll m) {
	return a * b % m;
}
ll qpow(ll x, ll y) {
	ll ans = 1, res = x % mod ;
	while(y) {
		if(y & 1)
			ans = bigmul(ans, res, mod);
		res = bigmul(res, res, mod);
		y >>= 1 ;
	}
	return ans;
}
ll c(ll x, ll y) {
	if(x < y)
		return 0;
	//cout << "c(" << x << ", " << y << ") = " << fac[x] << "-" << inv[y] << "-" << inv[x - y] << "\n";
	return fac[x] * inv[y] % mod * inv[x - y] % mod;
}
int main() {
	//freopen("ex_seq3.out", "w", stdin);
	for(ll i = 1 ; i <= N - 10 ; i++)
		p[i] = p[i - 1] * 2 % mod;
	scanf("%lld", &n);
	for(ll i = 1 ; i <= n ; i++) {
		scanf("%lld", a + i);
		bu[a[i]]++;
	}
	for(ll i = 1 ; i <= N - 10 ; i++)
		fac[i] = fac[i - 1] * i % mod;
	//*
	inv[N - 10] = qpow(fac[N - 10], mod - 2);
	//cout << inv[n] << "\n";
	for(ll i = N - 11 ; i >= 0 ; i--) {
		inv[i] = (i + 1) * inv[i + 1] % mod;
		//cout << inv[i] << " " << inv[i] * fac[i] % mod << "\n";
		//cout << inv[i] - qpow(fac[i], mod - 2) << "\n";
	}
	//*/
	bool bj = true;
	for(int i = 1 ; i <= n ; i++) {
		if(!bu[i])
			bj = false;
		//bu[i] += bu[i - 1];
		//sum[i] = bu[i] + sum[i - 1];
	}
	//*
	if(bj){
		ll ans = 0;
		for(ll i = n, t = 1 ; i ; i--, t = (t * 2) % mod){
			ans += t;
			ans %= mod;
		}
		printf("%lld", ans);
		exit(0);
	}
	/*
	for(int i = 1 ; i <= n ; i++)
		for(int j = i ; j <= sum[i] ; j++)
			for(int x = 0 ; x <= bu[i] ; x++){
				f[i][j] += (f[i - 1][j - x] + (j - x <= i && i <= j)) * c(bu[i], x);
				f[i][j] %= mod;
			}
	for(int k = 1 ; k <= n ; k++)
		for(int i = 1 ; i <= sum[k] ; i++){
			cout << f[k][i] << " \n"[i == sum[k]];
		}
	//*/
	sort(a + 1, a + 1 + n);
	for(ll i = 1 ; i <= n ; i++) {
		ans[i] = c(i - 1, a[i] - 1) * p[n - i] % mod;
		//cout << i << " " << ans[i] << "\n";
	}
	ll ans1 = 0;
	for(int i = 1 ; i <= n ; i++)
		ans1 = (ans1 + ans[i]) % mod;
	printf("%lld", ans1);
	return 0;
}