#include <bits/stdc++.h>
using namespace std;

int ans = 10000;
int h, w;
vector<vector<char>> s(60, vector<char>(60, '#'));
vector<vector<int>> a(60, vector<int>(60, 10000));
int dx[] = {1,0,-1,0};
int dy[] = {0,1,0,-1};

void search(int cnt, int x, int y){
	a[x][y] = cnt;
	if(h==x && w==y){
		ans = min(cnt,ans);
		return;
	}
	for(int dir = 0; dir < 4; ++dir){
		int nx = x + dx[dir];
		int ny = y + dy[dir];
		if(s[nx][ny] == '.' && cnt+1<a[nx][ny])
			search(cnt+1, nx, ny);
	}
}


int main(void){
	cin >> h >> w;
	int bk = 0;
	for(int i = 1; i <= h; ++i){
		for(int j = 1; j <= w; ++j){
			cin >> s[i][j];
			if(s[i][j] == '#') bk++;
		}
	}
	search(1,1,1);
	cout << (a[h][w]!=10000?h*w-bk-ans:-1) << endl;
	return 0;
}