string dir;

int dxx[] = {1, 0, , 0, -1};
int dyy[] = {0, -1, 1, 0};

string dfs(int row , int col , int k)
{

    if(k == 0) return "";

    for(int i = 0 ; i < 4 ; i++){
        int x = row + dxx[i] , y = col + dyy[i];
        if(dis[x][y] < k){
            string ans = dfs(x, y , k-1);
            if(ans == "IMPOSSIBLE") return ans;
            return dir[i] + ans;
        }
    }
    return "IMPOSSIBLE";
}



int main()
{
    /// problem: https://codeforces.com/problemset/problem/769/C

    dir = "DLRU";

    for(int i = 0 ; i < n ; i++){
        for(int j = 0 ; j < m ; j++){
            if(str[i][j] == 'X'){
                bfs(i , j);
                cout<<dfs(i , j , k)<<endl;
                return 0;
            }
        }
    }