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//It is made by ljh2000
#include <iostream>
#include <cstdlib>
#include <cstring>
#include <cstdio>
#include <cmath>
#include <algorithm>
using namespace std;
typedef long long LL;
const int MOD = 400007;
const int MAXN = 200011;
const int Bas = 1000000007;
const int MAXM = 5000011;
int n,m,c,yi[12][2]={{1,0},{0,1},{-1,0},{0,-1}};
int father[MAXM],ans,top;
LL dui[MAXM];
struct Cricket{ int x,y; }b[MAXN];
struct Hash{	
	int ecnt,first[MOD+12],next[MAXM];
	LL to[MAXM];
	inline void init(){ ecnt=0;	memset(first,0,sizeof(first)); }
	inline void insert(LL x,LL y){
		LL num=(x*Bas+y); int cc=(int)(num%MOD);
		next[++ecnt]=first[cc]; first[cc]=ecnt; to[ecnt]=num;
	}

	inline int query(LL x,LL y){
		LL num=(x*Bas+y); int cc=(int)(num%MOD);
		for(int i=first[cc];i;i=next[i]) if(to[i]==num) return i;
		return -1;
	}
}mp1,mp2;

inline int getint(){
    int w=0,q=0; char c=getchar(); while((c<‘0‘||c>‘9‘) && c!=‘-‘) c=getchar();
    if(c==‘-‘) q=1,c=getchar(); while (c>=‘0‘&&c<=‘9‘) w=w*10+c-‘0‘,c=getchar(); return q?-w:w;
}

namespace Graph{
	const int maxn = 2400011;
	const int maxm = 10000011;
	int ecnt,first[maxn],to[maxm],next[maxm],dfn[maxn],low[maxn],cnt,kcnt,stack[maxn],stack_top;
	bool iscut[maxn],yiji[maxn];
	inline void init(){	ecnt=0; memset(first,0,sizeof(first)); memset(yiji,0,sizeof(yiji)); }
	inline int find(int x){ if(father[x]!=x) father[x]=find(father[x]); return father[x]; }
	/*inline int find(int x){
		stack_top=0;
		while(father[x]!=x) {
			stack[++stack_top]=x;
			x=father[x];
		}
		while(stack_top>0) {
			father[stack[stack_top]]=x;
			stack_top--;
		}
		return x;
	}*/
	inline void link(int x,int y){ 
		next[++ecnt]=first[x]; first[x]=ecnt; to[ecnt]=y; 
		next[++ecnt]=first[y]; first[y]=ecnt; to[ecnt]=x;
	}
	inline void tarjan(int x,int fa){
		dfn[x]=low[x]=++cnt; int size=0;
		for(int i=first[x];i;i=next[i]) {
			int v=to[i]; if(v==fa) continue;
			if(dfn[v]==-1) {
				size++;	tarjan(v,x);
				low[x]=min(low[x],low[v]);
				if(low[v]>=dfn[x]) iscut[x]=1;
			}
			else if(low[v]<low[x]) low[x]=low[v];
		}
		if(fa==-1 && size==1) iscut[x]=0;
	}
	inline void work(){
		if((LL)n*m-c==2 && mp2.ecnt==2) { if(to[first[1]]==2) { puts("-1"); return ; } }//特判只有相邻的两个的情况
		for(int i=1;i<=mp2.ecnt;i++) dfn[i]=low[i]=-1,iscut[i]=0; cnt=0; kcnt=0;
		for(int i=1;i<=mp2.ecnt;i++) if(dfn[i]==-1) { kcnt++,tarjan(i,-1); }
		if(n==1 || m==1) { puts("1"); return ; }//特判n、m等于1的情况
		for(int i=1;i<=mp2.ecnt;i++) if(yiji[i] && iscut[i]) { puts("1"); return ; }
		puts("2");
	}
}

inline void build(int inx,int iny){
	int nowx,nowy,nx,ny,nn;
	for(int i=-2;i<=2;i++)
		for(int j=-2;j<=2;j++) {
			if(i==0 && j==0) continue;
			nowx=inx+i; nowy=iny+j; if(nowx<=0 || nowy<=0 || nowx>n || nowy>m) continue;
			if(mp1.query(nowx,nowy)!=-1) continue; nn=mp2.query(nowx,nowy);
			if(nn!=-1) { if(abs(i)<=1 && abs(j)<=1) Graph::yiji[nn]=1;  continue; } 
			mp2.insert(nowx,nowy); nn=mp2.query(nowx,nowy);
			if(abs(i)<=1 && abs(j)<=1) Graph::yiji[nn]=1;
			for(int l=0;l<4;l++) {
				nx=nowx+yi[l][0]; ny=nowy+yi[l][1]; if(nx<=0 || ny<=0 || nx>n || ny>m) continue;
				if(mp1.query(nx,ny)!=-1) continue; if(mp2.query(nx,ny)==-1) continue;
				Graph::link(nn,mp2.query(nx,ny));
			}
		}
}

inline void check_init(){
	using namespace Graph;
	int r1,r2; for(int i=1;i<=mp2.ecnt;i++) father[i]=i;
	for(int i=1;i<=mp2.ecnt;i++)
		for(int j=first[i];j;j=next[j]) {
			if(to[j]<=i) continue;
			r1=find(i); r2=find(to[j]);
			if(r1!=r2) father[r1]=r2;
		}
}

inline void check(int inx,int iny){
	using namespace Graph;
	int nowx,nowy; top=0;
	for(int i=-2;i<=2;i++)
		for(int j=-2;j<=2;j++){
			if(i==0 && j==0) continue;
			nowx=inx+i; nowy=iny+j; if(nowx<=0 || nowy<=0 || nowx>n || nowy>m) continue;
			if(mp1.query(nowx,nowy)!=-1) continue;
			dui[++top]=mp2.query(nowx,nowy);
		}
	for(int i=2;i<=top;i++) if(find(dui[i])!=find(dui[1])) { ans=0; return ; }
}

inline void work(){
	int T=getint();
	while(T--) {
		n=getint(); m=getint(); c=getint(); 
		for(int i=1;i<=c;i++) b[i].x=getint(),b[i].y=getint();
		if((LL)n*m-c<=1) { puts("-1"); continue; }//特判无解
		if(c==0 && n*m==2) { puts("-1"); continue; }//特判只有相邻的两个的情况
		mp1.init(); mp2.init(); Graph::init(); ans=-1;
		for(int i=1;i<=c;i++) mp1.insert(b[i].x,b[i].y);
		for(int i=1;i<=c;i++) build(b[i].x,b[i].y);		
		//检查0的情况
		check_init(); 
		for(int i=1;i<=c;i++) { check(b[i].x,b[i].y); if(ans==0) break; }
		if(ans==0) { puts("0"); continue; }
		Graph::work();
	}
}

int main()
{
    work();
    return 0;
}