#include<cstdio>

#include<iostream>

#define ll long long

#define R register ll

using namespace std;

inline ll g() {

    R ret=,fix=; register char ch; while(!isdigit(ch=getchar())) fix=ch=='-'?-:fix;

    do ret=ret*+(ch^); while(isdigit(ch=getchar())); return ret*fix;

}

inline ll qpow(ll a,ll b,ll p) { R ret=; a%=p;

    for(;b;b>>=,(a*=a)%=p) if(b&) (ret*=a)%=p; return ret;

}

inline void exgcd(ll a,ll b,ll& x,ll& y) {

    if(!b) {x=,y=; return ;}

    exgcd(b,a%b,y,x),y-=a/b*x;

}

inline ll Inv(ll n,ll p) {

    R x,y; exgcd(n,p,x,y); return (x%p+p)%p;

}

ll n,m,p,w[];

inline ll fac(int n,int pi,int pk) {

    if(!n) return ; R ans=;

    for(R i=;i<pk;++i) if(i%pi) ans=ans*i%pk;//循环节

    ans=qpow(ans,n/pk,pk); //快速幂，即循环节的个数

    for(R i=;i<=n%pk;++i) if(i%pi) ans=ans*i%pk;//处理最后的散块

    return ans*fac(n/pi,pi,pk)%pk; //递归求解

}

inline ll L(int n,int m,int pi,int pk) {

    R ind=; for(R i=n;i;i/=pi) ind+=i/pi;

    for(R i=m;i;i/=pi) ind-=i/pi;

    for(R i=n-m;i;i/=pi) ind-=i/pi;

    R N=fac(n,pi,pk),M=fac(m,pi,pk),N_M=fac(n-m,pi,pk);

    return N*Inv(M,pk)%pk*Inv(N_M,pk)%pk*qpow(pi,ind,pk)%pk;

}

inline ll solve(int n,int m) { R tmp=p,ans=;

    for(R i=;i*i<=tmp;++i) if(tmp%i==) {

        R pk=; while(tmp%i==) pk*=i,tmp/=i;

        ans=(ans+L(n,m,i,pk)*Inv(p/pk,pk)%p*p/pk%p)%p;

    } if(tmp>) ans=(ans+L(n,m,tmp,tmp)*Inv(p/tmp,tmp)%p*p/tmp%p)%p;

    return ans;

}

signed main() {

    p=g(),n=g(),m=g(); R sum=;

    for(R i=;i<=m;++i) sum+=(w[i]=g());

    if(sum>n) {printf("Impossible\n"); return ;}

    R ans=; for(R i=;i<=m;++i) ans=ans*solve(n,w[i])%p,n-=w[i];

    printf("%lld\n",ans);

}