#include<cstdio>
#define N 100001
bool c[N];
int n,m,i,b[1000],j,t;
int main()
{FILE *f=fopen("grigo.in","r"),*g=fopen("grigo.out","w");
fscanf(f,"%d%d",&n,&m),b[0]=b[1]=1;
while(m--)
      fscanf(f,"%d",&i),c[i]=1;
for(i=1;i<=n;i++)
if(!c[i])
      {for(j=1,t=0;j<=b[0]||t;j++,t/=10)
             b[j]=(t+=b[j]*(i-1))%10;
      b[0]=j-1;}
for(j=b[0];j;j--)
      fprintf(g,"%d",b[j]);
return 0;}