// Slower C++ solution:
#define _USE_MATH_DEFINES

#define INF 0x3f3f3f3f

#include <cstdio>

#include <iostream>

#include <sstream>

#include <cmath>

#include <cstdlib>

#include <algorithm>

#include <queue>

#include <stack>

#include <limits>

#include <map>

#include <string>

#include <cstring>

#include <set>

#include <deque>

#include <bitset>

#include <list>

#include <cctype>

#include <utility>

 

using namespace std;

 

typedef long long ll;

typedef pair <int,int> P;

typedef pair <int,P > PP;

 

const static int tx[] = {+0,+1,+0,-1};

const static int ty[] = {-1,+0,+1,+0};

 

static const double EPS = 1e-12;



int W,H;

char stage[1001][1001];

bool visited[1001][1001];



class State{

public:

  int x;

  int y;

  int cost;

  State(int _x,int _y,int _c) : x(_x),y(_y),cost(_c){}



  bool operator <(const State& s) const{

    return cost < s.cost;

  }

  bool operator >(const State& s) const{

    return cost > s.cost;

  }

};



void bfs(){

  priority_queue<State,vector<State>,greater<State> > que;

  que.push(State(0,0,0));

  

  while(!que.empty()){

    State s = que.top();

    que.pop();

    int sx = s.x;

    int sy = s.y;

    if(visited[sy][sx]) continue;



    visited[sy][sx] = true;

    if(stage[sy][sx] == 't') break;

    for(int i=0;i<4;i++){

      int dx = sx + tx[i];

      int dy = sy + ty[i];

      if(dx < 0 || dy < 0 || dx >= W || dy >= H) continue;

      if(visited[dy][dx]) continue;

      if(stage[dy][dx] == '#') continue;

      que.push(State(dx,dy,s.cost+1));

    }

  }

}



void dfs(int sx,int sy){

  visited[sy][sx] = true;

  for(int i=0;i<4;i++){

    int dx = sx + tx[i];

    int dy = sy + ty[i];

    if(dx < 0 || dy < 0 || dx >= W || dy >= H) continue;

    if(visited[dy][dx]) continue;

    if(stage[dy][dx] == '#') continue;

    dfs(dx,dy);

  }

}



bool has_route(int time,const vector<P>& gates,

	       int gx,int gy){



  vector<P> skip;

  for(int i=0;i<time;i++){

    int x = gates[i].first;

    int y = gates[i].second;

    if(stage[y][x] == '.'){

      skip.push_back(gates[i]);

    }

    stage[y][x] = '.';

  }

  memset(visited,false,sizeof(visited));

  bfs();



  for(int i=0;i<time;i++){

    int x = gates[i].first;

    int y = gates[i].second;

    stage[y][x] = '#';

  }



  for(int i=0;i<skip.size();i++){

    int x = skip[i].first;

    int y = skip[i].second;

    stage[y][x] = '.';

  }

  return visited[gy][gx];

}



int main(){



  while(~scanf("%d %d",&W,&H)){



    int gx,gy;

    for(int y=0;y<H;y++){

      string line;

      cin >> line;

      for(int x=0;x<W;x++){

	stage[y][x] = line[x];

	if(line[x] == 't'){

	  gx = x;

	  gy = y;

	}

      }

    }



    vector<P> gates;

    int total_time;

    scanf("%d",&total_time);

    for(int time=0;time<total_time;time++){

      int x,y;

      scanf("%d %d",&x,&y);

      gates.push_back(P(x,y));

    }



    int min_time = 0;

    int max_time = gates.size();

    bool isok = false;

    for(int round=0;round<20;round++){

      int mid = (min_time + max_time) / 2;

      if(has_route(mid,gates,gx,gy)){

	max_time = mid;

	isok = true;

      }

      else{

	min_time = mid+1;

      }

    }



    printf("%d\n",isok ? max_time : -1);

  }

}

// Faster C++ solution for the same problem (measured speedup: 1.3720005851153165x):
#define _USE_MATH_DEFINES

#define INF 0x3f3f3f3f

#include <cstdio>

#include <iostream>

#include <sstream>

#include <cmath>

#include <cstdlib>

#include <algorithm>

#include <queue>

#include <stack>

#include <limits>

#include <map>

#include <string>

#include <cstring>

#include <set>

#include <deque>

#include <bitset>

#include <list>

#include <cctype>

#include <utility>

 

using namespace std;

 

typedef long long ll;

typedef pair <int,int> P;

typedef pair <int,P > PP;

 

const static int tx[] = {+0,+1,+0,-1};

const static int ty[] = {-1,+0,+1,+0};

 

static const double EPS = 1e-12;



int W,H;

char stage[1001][1001];

bool visited[1001][1001];



class State{

public:

  int x;

  int y;

  int cost;

  State(int _x,int _y,int _c) : x(_x),y(_y),cost(_c){}



  bool operator <(const State& s) const{

    return cost < s.cost;

  }

  bool operator >(const State& s) const{

    return cost > s.cost;

  }

};



void bfs(){

  priority_queue<State,vector<State>,greater<State> > que;

  que.push(State(0,0,0));

  

  while(!que.empty()){

    State s = que.top();

    que.pop();

    int sx = s.x;

    int sy = s.y;

    if(visited[sy][sx]) continue;



    visited[sy][sx] = true;

    if(stage[sy][sx] == 't') break;

    for(int i=0;i<4;i++){

      int dx = sx + tx[i];

      int dy = sy + ty[i];

      if(dx < 0 || dy < 0 || dx >= W || dy >= H) continue;

      if(visited[dy][dx]) continue;

      if(stage[dy][dx] == '#') continue;

      que.push(State(dx,dy,s.cost+1));

    }

  }

}



void dfs(int sx,int sy){

  visited[sy][sx] = true;

  for(int i=0;i<4;i++){

    int dx = sx + tx[i];

    int dy = sy + ty[i];

    if(dx < 0 || dy < 0 || dx >= W || dy >= H) continue;

    if(visited[dy][dx]) continue;

    if(stage[dy][dx] == '#') continue;

    dfs(dx,dy);

  }

}



bool has_route(int time,const vector<P>& gates,

	       int gx,int gy){



  vector<P> skip;

  for(int i=0;i<time;i++){

    int x = gates[i].first;

    int y = gates[i].second;

    if(stage[y][x] == '.'){

      skip.push_back(gates[i]);

    }

    stage[y][x] = '.';

  }

  memset(visited,false,sizeof(visited));

  bfs();



  for(int i=0;i<time;i++){

    int x = gates[i].first;

    int y = gates[i].second;

    stage[y][x] = '#';

  }



  for(int i=0;i<skip.size();i++){

    int x = skip[i].first;

    int y = skip[i].second;

    stage[y][x] = '.';

  }

  return visited[gy][gx];

}



int main(){



  while(~scanf("%d %d",&W,&H)){



    int gx,gy;

    for(int y=0;y<H;y++){

      string line;

      cin >> line;

      for(int x=0;x<W;x++){

	stage[y][x] = line[x];

	if(line[x] == 't'){

	  gx = x;

	  gy = y;

	}

      }

    }



    vector<P> gates;

    int total_time;

    scanf("%d",&total_time);

    for(int time=0;time<total_time;time++){

      int x,y;

      scanf("%d %d",&x,&y);

      gates.push_back(P(x,y));

    }



    int min_time = 0;

    int max_time = gates.size();

    bool isok = false;

    for(int round=0;round<10;round++){

      int mid = (min_time + max_time) / 2;

      if(has_route(mid,gates,gx,gy)){

	max_time = mid;

	isok = true;

      }

      else{

	min_time = mid+1;

      }

    }



    printf("%d\n",isok ? max_time : -1);

  }

}