#define PII pair<int, int>
#define VI vector<int>

const int INFINIT = 1000000;

const int dx[5] = {0, 0, 1, -1};
const int dy[5] = {1, -1, 0, 0};

    start.first--, start.second--; // reindexam de la 0.
    queue<PII> Q;

    vector<VI> d(n, vector<int> (m, INFINIT));

    vector<VI> d(n, vector<int> (m, n * m));

    d[start.first][start.second] = 0;
    Q.push(start);