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//组合数取模
#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cmath>
#include <algorithm>

using namespace std;

const int MaxM = 10 + 5, MaxPi = 100000 + 5;

int n, m, Top;
int W[MaxM], Ci[MaxPi], Pi[MaxPi], Phi[MaxPi], PiCi[MaxPi]; 

typedef long long LL;

LL P, Q, Ans, Sum;
LL f[MaxPi], MI[MaxPi], PI[MaxPi];;

LL Pow(LL a, LL b, LL Mod) {
	a %= Mod; b %= Mod;
	LL ret = 1, f = a;
	while (b) {
		if (b & 1) {
			ret *= f;
			ret %= Mod;
		}
		b >>= 1;
		f *= f;
		f %= Mod;
	}
	return ret;
}

struct ES
{
	LL u, t;
};

ES Solve(int num, int Pi_e, int PiCi_e) {
	ES ret;
	ret.u = 0;
	ret.t = 1;
	while (num) {
		ret.u += num / Pi_e;
		ret.t *= Pow(f[PiCi_e - 1], num / PiCi_e, PiCi_e);
		ret.t %= PiCi_e;
		ret.t *= f[num % PiCi_e];
		ret.t %= PiCi_e;
		num /= Pi_e;
	}
	return ret;
}

LL C1(int a, int b, int Pi_e, int PiCi_e, int Phi_e) {
	f[0] = 1; f[1] = 1;
	for (int i = 2; i <= PiCi_e - 1; i++) {
		if (i % Pi_e == 0) f[i] = f[i - 1];
		else f[i] = f[i - 1] * i % PiCi_e;
	}
	LL ret, uu, t1, t2, t3;
	ES e1, e2, e3;
	e1 = Solve(a, Pi_e, PiCi_e);
	e2 = Solve(a - b, Pi_e, PiCi_e);
	e3 = Solve(b, Pi_e, PiCi_e);
	uu = e1.u - (e2.u + e3.u);
	t1 = e1.t; t2 = e2.t; t3 = e3.t;
	ret = Pow(Pi_e, uu, PiCi_e);
	ret *= t1; ret %= PiCi_e;
	ret *= Pow(t2, Phi_e - 1, PiCi_e); ret %= PiCi_e;
	ret *= Pow(t3, Phi_e - 1, PiCi_e); ret %= PiCi_e;
	return ret;
}

LL C2(int a, int b) {
	LL ret;
	ret = 0;
	for (int i = 1; i <= Top; i++) {
		ret += (C1(a, b, Pi[i], PiCi[i], Phi[i]) * ((MI[i] * PI[i]) % P)) % P;
		ret %= P;
	}
	return ret;
}

int main()
{
	cin >> P >> n >> m;
	Sum = 0;
	for (int i = 1; i <= m; i++) {
		scanf("%d", &W[i]);
		Sum += (LL)W[i];
	}
	if (Sum > n) {
		printf("Impossible\n");
		return 0;
	}
	Top = 0;
	Q = P;
	int SQRTQ = (int)sqrt(Q * 1.0);
	for (int i = 2; i <= SQRTQ; i++) {
		if (Q % i != 0) continue;
		Pi[++Top] = i;
		PiCi[Top] = 1;
		Ci[Top] = 0;
		while (Q % i == 0) {
			++Ci[Top];
			PiCi[Top] *= i;
			Q /= i;
		}
		Phi[Top] = PiCi[Top] / i * (i - 1);
		MI[Top] = P / PiCi[Top];
		PI[Top] = Pow(MI[Top], Phi[Top] - 1, PiCi[Top]);
	}
	if (Q > 1) {
		Pi[++Top] = Q;
		PiCi[Top] = Q;
		Ci[Top] = 1;
		Phi[Top] = Q - 1;
		MI[Top] = P / PiCi[Top];
		PI[Top] = Pow(MI[Top], Phi[Top] - 1, PiCi[Top]);
	}
	Ans = 1;
	for (int i = 1; i <= m; i++) {
		Ans *= C2(n, W[i]);
		Ans %= P;
		n -= W[i];
	}
	cout << Ans << endl;
//	printf("%I64d\n", C2(n, m));
	return 0;
}