a[100],b[100001],C,N,i,k;

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