RT，wrong answer On line 1 column 1, read N,expected 3

#include<bits/stdc++.h>
using namespace std;
const int size=9000010;
int n,m,S,T;
int a[2001][2001];
int dx[]={-1,0,1,0};
int dy[]={0,-1,0,1};
int tot=0,ver[size],nxt[size],head[size];
inline int encode(int x,int y){
	return (x-1)*m+y;
}
inline void add(int x,int y){
	ver[++tot]=y,nxt[tot]=head[x],head[x]=tot;
	ver[++tot]=x,nxt[tot]=head[y],head[y]=tot;
}
int d[size],v[size];
priority_queue<pair<int,int>,vector<pair<int,int> >,greater<pair<int,int> > > q;
inline int dijkstra(){
	memset(d,0x3f,sizeof(d));
	d[S]=0;q.push(make_pair(0,S));
	while(!q.empty()){
		pair<int,int> tmp=q.top();q.pop();
		int x=tmp.second;
		if(v[x]) continue;
		v[x]=1;
		for(int i=head[x];i;i=nxt[i]){
			int y=ver[i];
			if(d[y]>d[x]+1){
				d[y]=d[x]+1;
				q.push(make_pair(d[y],y));
			}
		}
	}
	if(d[T]>=0x3f3f3f3f){
		cout<<"No Way!\n";
		exit(0);
	}
	return d[T];
}
int main(){
	ios::sync_with_stdio(0);
	cin>>n>>m;
	for(int i=1;i<=n;++i){
		string s;
		cin>>s;
		for(int j=0;j<m;++j){
			if(s[j]=='#') a[i][j+1]=0;
			else a[i][j+1]=1;
			if(s[j]=='m') S=encode(i,j+1);
			if(s[j]=='d') T=encode(i,j+1);
		}
	}
	for(int i=1;i<=n;++i)
	 for(int j=1;j<=m;++j)
	  if(a[i][j])
	   for(int k=0;k<4;++k)
	    if(i+dx[k]>=1&&i+dx[k]<=n)
	     if(j+dy[k]>=1&&j+dy[k]<=m)
	      if(a[i+dx[k]][j+dy[k]])
	       add(encode(i,j),encode(i+dx[k],j+dy[k]));
	cout<<dijkstra();
	return 0;
}