#include <bits/stdc++.h>
using namespace std;
int fx[] = {1, 0, 0, -1};
int fy[] = {0, -1, 1, 0};
int n, m;
int data[1002][1002], dist[1002][1002];
void bfs(int sx, int sy) {
  for (int i = 0; i < 1002; i++) {
    for (int j = 0; j < 1002; j++) dist[i][j] = INT_MAX;
  }
  queue<int> q;
  q.push(sx);
  q.push(sy);
  dist[sx][sy] = 0;
  while (!q.empty()) {
    int u = q.front();
    q.pop();
    int v = q.front();
    q.pop();
    for (int i = 0; i < 4; i++) {
      int x = u + fx[i];
      int y = v + fy[i];
      if (x >= 0 && x < n && y >= 0 && y < m && data[x][y] == 0 &&
          dist[x][y] > dist[u][v] + 1) {
        dist[x][y] = dist[u][v] + 1;
        q.push(x);
        q.push(y);
      }
    }
  }
}
int main() {
  int k;
  scanf("%d", &n);
  scanf("%d", &m);
  scanf("%d", &k);
  int sx, sy;
  for (int i = 0; i < n; i++) {
    for (int j = 0; j < m; j++) {
      char ch;
      cin >> ch;
      if (ch == '*')
        data[i][j] = 1;
      else if (ch == 'X') {
        sx = i;
        sy = j;
      }
    }
  }
  if (k % 2 != 0) {
    cout << "IMPOSSIBLE\n";
    return 0;
  }
  bfs(sx, sy);
  vector<char> res;
  while (k > 0) {
    if (sx < n - 1 && dist[sx + 1][sy] < k) {
      sx++;
      res.push_back('D');
    } else if (sy > 0 && dist[sx][sy - 1] < k) {
      sy--;
      res.push_back('L');
    } else if (sy < m - 1 && dist[sx][sy + 1] < k) {
      sy++;
      res.push_back('R');
    } else if (sx > 0 && dist[sx - 1][sy] < k) {
      sx--;
      res.push_back('U');
    } else {
      cout << "IMPOSSIBLE\n";
      return 0;
    }
    k--;
  }
  for (int i = 0; i < res.size(); i++) {
    cout << res[i];
  }
  printf("\n");
  return 0;
}
