a[100],b[100001],C,N,i;main(m){
	scanf("%d%d",&C,&N);
	for(;i<N;i++)scanf("%d",a+i);
	*b=1;
	for(i=0;i<N;i++)for(m=a[i];m<=C;m++)if(b[m-a[i]]&&(!b[m]||b[m-a[i]]<b[m]))b[m]=b[m-a[i]]+1;
	C=!printf("%d\n",b[C]-1);
}