#pragma GCC optimize("Ofast,no-stack-protector,unroll-loops,fast-math")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4.1,sse4.2,avx,avx2,popcnt,tune=native")
#include <immintrin.h>
#include <emmintrin.h>
#define ford(i,a,n) for(i=a;i<=n;i++)
#define forb(i,n,a) for(i=n;i>=a;i--)
#pragma comment(linker, "/STACK:1024000000,1024000000") 
#pragma GCC optimize(2)
#include<bits/stdc++.h> 
#define ll long long
#define I128 __int128
#define ld long double
#define PB push_back
using namespace std;
const int MAXN=4e5+666,mod=998244353,N=505;//
const ll INF=0x7ffffffffffffff;
const double PI=acos(-1);
typedef pair<int,int> pii;
template<class T>inline void MAX(T &x,T y){if(y>x)x=y;}
template<class T>inline void MIN(T &x,T y){if(y<x)x=y;}
template<class T>inline void rd(T &x){x=0;char o,f=1;while(o=getchar(),o<48)if(o==45)f=-f;do x=(x<<3)+(x<<1)+(o^48);while(o=getchar(),o>47);x*=f;}
template<class T>inline T ksm(T x,T y){T ans=1;while(y>0){if(y&1)ans=ans*x%mod;x=x*x%mod;y>>=1;}return ans;}
template<class T>inline T GCD(T x,T y){if(x==1||y==1)return 1;if(y>x)swap(x,y);while(x%y!=0){x=x%y;swap(x,y);}return y;}
int x[1005][1005];
int ans;
struct T{int x,id; }a[MAXN];
int cmp(T t1,T t2){ return t1.x>t2.x; }
vector<int> v;
int cal1(int p){ if(p%2) return p*(p/2+1); return p*(p/2); }
int cal2(int p){ if(p%2) return cal2(p-1)+p*2-1; return p*p/4*3; }
int main()
{
	int m,n,i,j,k,t,mx,p; rd(t);
	while(t--)
	{
		rd(m); rd(n); mx=0;
		for(i=1;i<=n;i++)
		{
			rd(a[i].x);
			if(a[i].x>mx){ mx=a[i].x;  p=i; }
			a[i].id=i;
		}
		if(m==1){ cout<<"1\n"<<a[p].id<<"\n"; continue; }
		int l=2,r=1000;
		while(l<r)
		{
			int mid=l+r>>1;
		//	cout<<l<<" "<<r<<" "<<mid<<" "<<cal1(mid)<<"\n";
			if(cal1(mid)>=mx) r=mid;
			else l=mid+1;
		}
		ans=l;// cout<<l<<"***\n";
		l=2; r=1000;
		while(l<r)
		{
			int mid=l+r>>1;
			if(cal2(mid)>=m) r=mid;
			else l=mid+1;
		}
		MAX(ans,l);//cout<<l<<"***\n";
		for(i=1;i<=ans;i++) for(j=1;j<=ans;j++) x[i][j]=0;
		cout<<ans<<"\n";
		sort(a+1,a+n+1,cmp);
		int k=1;
		for(i=1;i<=ans;i+=2)
		{
			if(k>n) break;
			for(j=2;j<=ans;j+=2)
			{
				while(k<=n&&a[k].x==0) k++;
				if(k>n) break;
				x[i][j]=a[k].id; a[k].x--;
			}
		}
		for(i=1;i<=ans;i+=2)
		{
			if(k>n) break;
			for(j=1;j<=ans;j+=2)
			{
				while(k<=n&&a[k].x==0) k++;
				if(k>n) break;
				x[i][j]=a[k].id; a[k].x--;
			}
		}
		for(i=2;i<=ans;i+=2)
		{
			if(k>n) break;
			for(j=1;j<=ans;j+=2)
			{
				while(k<=n&&a[k].x==0) k++;
				if(k>n) break;
				x[i][j]=a[k].id; a[k].x--;
			}
		}
		for(i=1;i<=ans;i++)
		{ for(j=1;j<=ans;j++) cout<<x[i][j]<<" "; cout<<"\n"; }
	}
}