ABC369F.cpp

/*
 * @FilePath: \c++\ABC369F.cpp
 * @Author: WRT_Partisan
 * @Date: 2026-02-02 18:02:55
 */
#include <bits/stdc++.h>
using namespace std;
#define int long long
int lowbit(int x) { return x & (-x); }
struct Node
{
    int x, y;
} c[200005];
struct BIT
{
    int M;
    vector<int> s, id;
    BIT(int x) : M(x) { s.assign(M + 1, 0), id.assign(M + 1, 0); }
    void update(int p, int w, int idx)
    {
        for (int i = p; i <= M; i += lowbit(i))
            if (s[i] < w)
                s[i] = w, id[i] = idx;
    }
    pair<int, int> ask(int p)
    {
        int res = 0, idx = 0;
        for (int i = p; i > 0; i -= lowbit(i))
            if (s[i] > res)
                res = s[i], idx = id[i];
        return {res, idx};
    }
};
int n, m, k, x, y, pre[200005], dp[200005];
void dfs(int p)
{
    if (pre[p] == -1)
        return;
    dfs(pre[p]);
    for (int i = c[pre[p]].x; i < c[p].x; i++)
        cout << 'D';
    for (int i = c[pre[p]].y; i < c[p].y; i++)
        cout << 'R';
}
signed main()
{
    cin.tie(0)->sync_with_stdio(0);
    cin >> n >> m >> k;
    for (int i = 1; i <= k; i++)
        cin >> c[i].x >> c[i].y;
    c[++k] = {n, m}, c[++k] = {1, 1};
    sort(c + 1, c + k + 1, [](Node a, Node b)
         { return a.x < b.x || (a.x == b.x && a.y < b.y); });
    BIT bt(m);
    dp[1] = 1, pre[1] = -1, bt.update(1, 1, 1);
    for (int i = 2; i <= k; i++)
    {
        auto t = bt.ask(c[i].y);
        dp[i] = t.first + 1, pre[i] = t.second, bt.update(c[i].y, dp[i], i);
    }
    cout << dp[k] - 2 << "\n";
    dfs(k);
    return 0;
}