#include<cstdio>

#include<cstring>

#include<cmath>

#include<queue>

#include<algorithm>

using namespace std;

const int maxn=+;

char s[maxn][maxn];

char tmp[maxn][maxn];

bool flag[maxn][maxn];

int dir[][]={

 {,},

 {,-},

 {,},

 {-,}

};

struct X

{

    int x,y;

}q[maxn*maxn];

int n,m,Q;

void read()

{

    scanf("%d%d",&n,&m);

    for(int i=;i<n;i++) scanf("%s",s[i]);

    scanf("%d",&Q);

    for(int i=;i<=Q;i++) scanf("%d%d",&q[i].x,&q[i].y);

}

bool P(int a,int b)

{

    if(a>=&&a<n)

    {

        if(b>=&&b<m)

        {

            if(tmp[a][b]=='')

            {

                if(flag[a][b]==)

                {

                    return ;

                }

            }

        }

    }

    return ;

}

void dfs(int x,int y)

{

    flag[x][y]=;

    for(int i=;i<;i++)

    {

        int newx=x+dir[i][];

        int newy=y+dir[i][];

        if(P(newx,newy)) dfs(newx,newy);

    }

}

bool f(int year)

{

    for(int i=;i<n;i++)

        for(int j=;j<m;j++)

            tmp[i][j]=s[i][j];

    for(int i=;i<=year;i++) tmp[q[i].x][q[i].y]='';

    bool fail=;

    for(int j=;j<m;j++) if(tmp[][j]=='') fail=;

    if(fail) return ;

    fail=;

    for(int j=;j<m;j++) if(tmp[n-][j]=='') fail=;

    if(fail) return ;

    memset(flag,,sizeof flag);

    for(int j=;j<m;j++)

        if(tmp[][j]=='')

            dfs(,j);

    fail=;

    for(int j=;j<m;j++)

        if(tmp[n-][j]==''&&flag[n-][j]==) fail=;

    return fail;

}

int main()

{

    int T;

    scanf("%d",&T);

    while(T--)

    {

        read();

        if(f()) printf("0\n");

        else

        {

            int ans=-;

            int left=,right=Q;

            while(left<=right)

            {

                int mid=(left+right)/;

                if(f(mid))

                {

                    ans=mid;

                    right=mid-;

                }

                else

                {

                    left=mid+;

                }

            }

            printf("%d\n",ans);

        }

    }

    return ;

}