void rec( ll i, ll j, ll i2, ll j2, ll x, ll y, ll dx, ll dy ) {
    for( ; x < n && y < m && x >= 0 && y >= 0 && b[x][y]; x += dx, y += dy ) {
        if( dx == 1 && dy == 0 ) {
            if( y + 1 < m && b[x][y + 1] && abs( i - x ) > 1 )
                rec( i, j, i, j, x, y, 0, 1 );
        } else if( dx == 0 && dy == 1 ) {
            if( x - 1 >= 0 && b[x - 1][y] && abs( j - y ) > 1 )
                rec( i, j, x, y, x, y, -1, 0 );
        } else if( dx == -1 && dy == 0 ) {
            if( y - 1 >= 0 && b[x][y - 1] )
                rec( i, j, i2, j2, x, y, 0, -1 );
        } else {
            if( x == i && y == j && abs( i - i2 ) > 1 && abs( j - j2 ) > 1 ) {
                ans.pb( mp( mp( i, j ), mp( i2, j2 ) ) );
                s.pb( f( ans[ans.size() - 1], false ) );
                f( ans[ans.size() - 1], true );
                return;
            }
        }
    }
}