#include<bits/stdc++.h>

using namespace std;

int dis[1005][1005];

string str[1005];

const string order = "DLRU";

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

void bfs(int row , int col)
{
    memset(dis,-1,sizeof dis);
    queue < pair < int , int > > que;
    que.push({row,col});
    dis[row][col] = 0;
    while(!que.empty()){
        row = que.front().first , col = que.front().second;
        que.pop();
        for(int i = 0 ; i < 4 ; i++){
            int x = row + dxx[i] , y = col + dyy[i];
            if(dis[x][y] == -1 && str[x][y] != '*'){
                dis[x][y] = dis[row][col] + 1;
                que.push({x,y});
            }
        }
    }

}



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

int main()
{
    /// problem B
    int n , m , k;
    cin>>n>>m>>k;
    for(int i = 1 ; i <= n ; i++){
        cin>>str[i];
        str[i] = "*" + str[i] + "*";
    }
    for(int i = 0 ; i < m+2 ; i++) str[0] += "*";
    str[n+1] = str[0];
//    for(int i = 0 ; i <= n+1 ; i++) cout<<str[i]<<endl;
    for(int i = 1 ; i <= n ; i++){
        for(int j = 1 ; j <= m ; j++){
            if(str[i][j] == 'X'){
                bfs(i,j);
//                cout<<"okay\n";
                string ans = dfs(i , j , k);
                cout<<ans<<endl;
                return 0;
            }
        }
    }
}