#include<bits/stdc++.h>

using namespace std;

#define rep0(i,l,r) for(int i = (l);i < (r);i++)

#define rep1(i,l,r) for(int i = (l);i <= (r);i++)

#define rep_0(i,r,l) for(int i = (r);i > (l);i--)

#define rep_1(i,r,l) for(int i = (r);i >= (l);i--)

#define MS0(a) memset(a,0,sizeof(a))

#define MS1(a) memset(a,-1,sizeof(a))

#define MSi(a) memset(a,0x3f,sizeof(a))

#define inf 0x3f3f3f3f

#define lson l, m, rt << 1

#define rson m+1, r, rt << 1|1

typedef pair<int,int> PII;

#define A first

#define B second

#define MK make_pair

typedef __int64 ll;

typedef unsigned int uint;

template<typename T>

void read1(T &m)

{

    T x=,f=;char ch=getchar();

    while(ch<''||ch>''){if(ch=='-')f=-;ch=getchar();}

    while(ch>=''&&ch<=''){x=x*+ch-'';ch=getchar();}

    m = x*f;

}

template<typename T>

void read2(T &a,T &b){read1(a);read1(b);}

template<typename T>

void read3(T &a,T &b,T &c){read1(a);read1(b);read1(c);}

template<typename T>

void out(T a)

{

    if(a>) out(a/);

    putchar(a%+'');

}

int T,kase = ,i,j,k,n,m;

const int N = ;

char s[N][N];

queue<PII> pq;

inline bool check(int nx,int ny)

{

    if(nx <  || nx >= n || ny <  || ny >= m) return false;

    return true;

}

int dir[][] = {{,,,-},{,,-,}};

int f[N*N];

int Find(int a){return a==f[a]?f[a]:f[a]=Find(f[a]);}

void _union(int a,int b){int p = Find(a),q = Find(b);f[p] = q;}

int idx(int r,int c) {return r*m+c;}

void BFS(int r,int c)

{

    pq.push({r,c});

    int d = Find(idx(r,c));

    while(!pq.empty()){

        r = pq.front().A,c = pq.front().B;pq.pop();

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

            int x = r + dir[][i] , y = c + dir[][i];

            int id = Find(idx(x,y));

            if(!check(x,y) || s[x][y] == '' || id == d) continue;

            f[id] = d;

            pq.push({x,y});

        }

    }

}

int x[N*N],y[N*N];

int main()

{

    //freopen("data.txt","r",stdin);

    //freopen("out.txt","w",stdout);

    read1(T);

    while(T--){

        read2(n,m);

        int tot = n*m;

        rep1(i,,tot+) f[i] = i;

        rep0(i,,n) scanf("%s",s[i]);

        int Q;

        read1(Q);

        rep1(i,,Q){

            read2(x[i],y[i]);

            s[x[i]][y[i]] = '';

        }

        rep0(i,,n) rep0(j,,m)if(s[i][j] == ''){

            int index = idx(i,j);

            if(f[index] == index){

                BFS(i,j);

            }

        }

        rep0(i,,m) _union(i,tot+);

        rep0(i,,m) _union(idx(n-,i),tot+);

        if(f[tot+] == f[tot+]){

            puts("-1");

            continue;

        }

        rep_1(i,Q,){

            s[x[i]][y[i]] = '';

            BFS(x[i],y[i]);

            if(Find(tot+) == Find(tot+)){

                out(i);

                puts("");

                break;

            }

        }

    }

    return ;

}