#include <iostream>
#include <set>
#include <list>
int width, height;
int table[7][7];

const int UP = 1, DOWN = 2, LEFT = 3, RIGHT = 4;
struct State{
  int sch_x, sch_y, cargo_x, cargo_y;
  int count;
  State(int a, int b, int c, int d): sch_x(a), sch_y(b), 
				     cargo_x(c), cargo_y(d), count(0){}
  bool operator < (const State & s) const {
    if(sch_x != s.sch_x){return sch_x < s.sch_x;}
    if(sch_y != s.sch_y){return sch_y < s.sch_y;}
    if(cargo_x != s.cargo_x){return cargo_x < s.cargo_x;}
    if(cargo_y != s.cargo_y){return cargo_y < s.cargo_y;}
    return false;
  }
};
struct less2{
  bool operator () (const State & s, const State & t) {
    if(s.count != t.count){return s.count < t.count;}
    return s < t;
  }
};

bool out_of_range(int x, int y){
  if(x < 0 || y < 0 || x >= width || y >= height){return true;}
  return table[y][x] == 1;
}

bool canGo(const State & s, int direction, State * newState){
  int dxs[] = {0, 0, 0, -1, 1};
  int dys[] = {0, -1, 1, 0, 0};
  int dx = dxs[direction];
  int dy = dys[direction];
  int cargo_dx = 0;
  int cargo_dy = 0;
  int dcount = 0;
  if(out_of_range(dx + s.sch_x, dy + s.sch_y)){
    return false;
  }
  if(dx + s.sch_x == s.cargo_x && dy + s.sch_y == s.cargo_y){
    if(out_of_range(dx * 2 + s.sch_x, dy * 2 + s.sch_y)){
      return false;
    }
    cargo_dx = dx;
    cargo_dy = dy;
    dcount = 1;
  }
  if(newState){
    newState->sch_x = s.sch_x + dx;
    newState->sch_y = s.sch_y + dy;
    newState->cargo_x = s.cargo_x + cargo_dx;
    newState->cargo_y = s.cargo_y + cargo_dy;
    newState->count = s.count + dcount;
  }
  return true;
}


int main(){
  while(true){
    std::cin >> width >> height;
    if(width == 0 && height == 0){break;}
    State s(0, 0, 0, 0);
    for(int i = 0; i < height; i++){
      for(int j = 0; j <  width; j++){
	std::cin >> table[i][j];
	if(table[i][j] == 2){
	  s.cargo_x = j;
	  s.cargo_y = i;
	}
	if(table[i][j] == 4){
	  s.sch_x = j;
	  s.sch_y = i;
	}
      }
    }
    std::set<State> cache;
    std::set<State, less2> q;
    cache.insert(s);
    q.insert(s);
    State newState(0, 0, 0, 0);
    while(!q.empty()){
      //std::cout << q.size() << ", " << cache.size() << std::endl;
      s = *q.begin();
      if(table[s.cargo_y][s.cargo_x] == 3){break;}
      q.erase(q.begin());
      for(int direction = 1; direction <= 4; direction++){
	if(canGo(s, direction, &newState)){
	  if(cache.find(newState) == cache.end()){
	    cache.insert(newState);
	    q.insert(newState);
	  }
	}
      }
    }
    std::cout << (q.empty() ? (-1): s.count) << std::endl;
  }
}