abc088 <bfs 最短路>

// https://atcoder.jp/contests/abc088/tasks/abc088_d
#include <iostream>
#include <algorithm>
#include <vector>
#include <cstring>
#include <queue>
using namespace std;
using LL = long long;
using PII = pair<int, int>;
const int N = 55;
int dis[N][N];
char g[N][N];
int dx[] = {-1, 1, 0, 0};
int dy[] = {0, 0, 1, -1};

void solv()
{
    int n, m;
    cin >> n >> m;
    for (int i = 1; i <= n; i ++) cin >> (g[i] + 1);

    int cntw = 0;
    for (int i = 1; i <= n; i ++)
        for (int j = 1; j <= m; j ++)
            if (g[i][j] == '.') cntw ++;
    
    if (g[1][1] == '#') {cout << -1; return; };
    queue<PII> q;
    q.push({1, 1}); dis[1][1] = 1;
    while (q.size())
    {
        auto [x, y] = q.front(); q.pop();
        for (int i = 0; i < 4; i ++)
        {
            int xx = x + dx[i], yy = y + dy[i];
            if (xx < 1 || xx > n || yy < 1 || yy > m || dis[xx][yy] || g[xx][yy] == '#') continue;
            dis[xx][yy] = dis[x][y] + 1;
            q.push({xx, yy});
        }
    }
    if (dis[n][m]) cout << cntw - dis[n][m] << endl;
    else cout << -1 << endl;
}

int main()
{
    ios::sync_with_stdio(false); cin.tie(0); cout.tie(0);
    int T = 1;
	// cin >> T;
    while (T --)
    {
        solv();
    }
    return 0;
}