#include<cstdio>
#include<cstring>
#include<queue>
using namespace std;
typedef long long ll;
const int dx[4]={0,1,0,-1};
const int dy[4]={1,0,-1,0};
const int P=1000117;
const int N=100050;
char rB[1<<21],*rS,*rT;
inline char gc(){return rS==rT&&(rT=(rS=rB)+fread(rB,1,1<<21,stdin),rS==rT)?EOF:*rS++;}
inline int rd(){
    char c=gc();
    while(c<48||c>57)c=gc();
    int x=c&15;
    for(c=gc();c>=48&&c<=57;c=gc())x=(x<<3)+(x<<1)+(c&15);
    return x;
}
int x[N],y[N],G[N*24],to[N*192],nxt[N*192],sz,cnt,pre[N*24],dfsc,n,m,c,tmpx[N*24],tmpy[N*24],ctmp;
bool isok[N*24],iscut[N*24];
struct node{
	int x,y;
	node(){}
	node(int x,int y):x(x),y(y){}
};
queue<node> Q,q;
struct Hash{  //��hashʵ��map
	int h[P],vx[N*25],vy[N*25],p[N*25],nxt[N*25],sz;
	inline void clear(){
		memset(h,0,sizeof(h));sz=0;
	}
	inline void ins(int x,int y,int id){
		int pos=((ll)(x-1)*n+y-1)%P;
		vx[++sz]=x;vy[sz]=y;p[sz]=id;nxt[sz]=h[pos];h[pos]=sz;
	}
	inline int ask(int x,int y){
		for(int k=h[((ll)(x-1)*n+y-1)%P];k;k=nxt[k])if(vx[k]==x&&vy[k]==y)return p[k];
		return 0;
	}
}h,col,tem;
inline int Abs(int x){return x<0?-x:x;}
inline int Max(int a,int b){return a>b?a:b;}
inline void add(int u,int v){
	to[++sz]=v;nxt[sz]=G[u];G[u]=sz;
	to[++sz]=u;nxt[sz]=G[v];G[v]=sz;
}
inline bool check(){
	int i,j,k,tx,ty;
	for(i=1;i<=n;++i)
		for(j=1;j<=m;++j)if(!h.ask(i,j)){
			for(k=0;k<4;++k)if((tx=i+dx[k])&&tx<=n&&(ty=j+dy[k])&&ty<=m&&!h.ask(tx,ty))return 1;
			return 0;
		}
}
inline void bfs(int sx,int sy,int cl){  //��һ��floodfill
	int i,u,v,tx,ty;
	q.push(node(sx,sy));col.ins(sx,sy,cl);
	while(!q.empty()){
		u=q.front().x;v=q.front().y;q.pop();
		for(i=0;i<4;++i)if((tx=u+dx[i])&&tx<=n&&(ty=v+dy[i])&&ty<=m&&h.ask(tx,ty)>0&&!col.ask(tx,ty)){
			col.ins(tx,ty,cl);  //��col����¼������ͨ����（Ҳ��Ϊ��ɫ）
			q.push(node(tx,ty));
		}
	}
}
inline bool bfs2(int sx,int sy){
	int i,u,v,x,y,t;
	q.push(node(sx,sy));tem.ins(sx,sy,-1);
	while(!q.empty()){
		u=q.front().x;v=q.front().y;q.pop();
		for(x=Max(1,u-1);x<=n&&x<=u+1;++x)
			for(y=Max(1,v-1);y<=m&&y<=v+1;++y)if((t=h.ask(x,y))&&!tem.ask(x,y))if(t==-1){
				tem.ins(x,y,-1);  //��tem����ֹ���ϰ�����ظ�����
//����������ظ���������ܹ�c*8��，����Ӱ�츴�Ӷ�
				q.push(node(x,y));
			}else{tmpx[++ctmp]=x;tmpy[ctmp]=y;}
	}
	if(ctmp==-1)return 1;
	for(i=1,t=col.ask(tmpx[0],tmpy[0]);i<=ctmp;++i)if(col.ask(tmpx[i],tmpy[i])!=t)return 0;
	return 1;
}
inline bool ncon(){  //�ж��Ƿ���ͨ
	int i,u,v,ccl=0;
	col.clear();
	while(!Q.empty()){
		u=Q.front().x;v=Q.front().y;Q.pop();
		if(col.ask(u,v))continue;
		bfs(u,v,++ccl);
	}
	tem.clear();
	for(i=0;i<c;++i)if(!tem.ask(x[i],y[i])){
		ctmp=-1;
		if(!bfs2(x[i],y[i]))return 1;
	}
	return 0;
}
int dfs(int u,int fa){  //dfs��
	int i,v,lowu=pre[u]=++dfsc,lowv,chd=0;
	for(i=G[u];i;i=nxt[i])if((v=to[i])!=fa)if(!pre[v]){
		++chd;
		if((lowv=dfs(v,u))>=pre[u])iscut[u]=1;
		if(lowv<lowu)lowu=lowv;
	}else if(pre[v]<lowu)lowu=pre[v];
	if(!fa&&chd==1)iscut[u]=0;
	return lowu;
}
int main(){
	int T=rd(),i,j,k,l,t,tt,tx,ty;
	bool ok;
	while(T--){
		n=rd();m=rd();c=rd();
		h.clear();
		for(i=0;i<c;++i){
			x[i]=rd();y[i]=rd();
			h.ins(x[i],y[i],-1);
		}
		if((ll)n*m-c<2ll){
			puts("-1");
			continue;
		}
		if((ll)n*m-c==2ll){
			puts(check()?"-1":"0");
			continue;
		}
		memset(G,0,sizeof(G));ok=sz=cnt=dfsc=0;
		memset(pre,0,sizeof(pre));
		memset(iscut,0,sizeof(iscut));
		memset(isok,0,sizeof(isok));
        //��ͼ
		for(i=0;i<c;++i)
			for(j=Max(1,x[i]-2);j<=x[i]+2&&j<=n;++j)
				for(k=Max(1,y[i]-2);k<=y[i]+2&&k<=m;++k)if(!(t=h.ask(j,k))){
					h.ins(j,k,++cnt);Q.push(node(j,k));
					isok[cnt]=Max(Abs(j-x[i]),Abs(k-y[i]))<=1;
					for(l=0;l<4;++l)if((tx=j+dx[l])&&tx<=n&&(ty=k+dy[l])&&ty<=m&&(tt=h.ask(tx,ty))>0)add(cnt,tt);
				}else if(t>0&&Max(Abs(j-x[i]),Abs(k-y[i]))<=1)isok[t]=1;
		if(ncon()){
			puts("0");
			continue;
		}
		if(n==1||m==1){  //һ�л�һ�п�������
			puts("1");
			continue;
		}
		for(i=1;i<=cnt;++i){
			if(!pre[i])dfs(i,0);
			if(isok[i]&&iscut[i]){
				puts("1");
				ok=1;break;
			}
		}
		if(!ok)puts("2");
	}
	return 0;
}