E 19.08.13

#include <stdio.h>
#include <math.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include <bitset>
#include <iostream>
#include <stack>
#include <queue>
#include <set>
#include <map>
#include <string>
#include <algorithm>
using namespace std;


int main() {
    freopen("input.txt", "r", stdin);
    freopen("output.txt", "w", stdout);

    scanf("%d\n%s", &n, s);

    for (int j = 0; j < 64; j++) {
        d[0][j] = p[0][j] = -1;
    }
    d[0][f(c('L'), c('R'), 0, 0)] = 0;
    for (int i = 1; i <= n; i++) {
        for (int j = 0; j < 64; j++) {
            d[i][j] = 1 << 30;
            p[i][j] = -1;
        }
    }

    for (int i = 1; i <= n; i++) {
        for (int j = 0; j < 64; j++) {
            if (d[i - 1][j] == -1)
                continue;
            u(i, j, f(l(j), r(j), 0, 0), 0);
            u(i, j, f(l(j), r(j), 1, 0), 1);
            u(i, j, f(l(j), r(j), 0, 1), 1);
            if (!lp(j)) {
                for (int p = 0; p < 4; p++) {
                    if (p == l(j) || p == r(j))
                        continue;
                    u(i, j, f(p, r(j), 1, 0), 3);
                }
            } else {
                for (int p = 0; p < 4; p++) {
                    if (p == l(j) || p == r(j))
                        continue;
                    u(i, j, f(p, r(j), 1, 0), 9);
                }
            }
            if (!rp(j)) {
                for (int p = 0; p < 4; p++) {
                    if (p == l(j) || p == r(j))
                        continue;
                    u(i, j, f(l(j), p, 0, 1), 3);
                }
            } else {
                for (int p = 0; p < 4; p++) {
                    if (p == l(j) || p == r(j))
                        continue;
                    u(i, j, f(l(j), p, 0, 1), 9);
                }
            }
            for (int p1 = 0; p1 < 4; p1++) {
                for (int p2 = 0; p2 < 4; p2++) {
                    if (p1 == p2)
                        continue;
                    u(i, j, f(p1, p2, 1, 1), 10);
                }
            }
        }

        for (int j = 0; j < 64; j++) {
            if ((l(j) == c('R') && r(j) == c('L')) ||
                (l(j) == r(j)) ||
                (s[i - 1] != 'N' && l(j) != c(s[i - 1]) && r(j) != c(s[i - 1])) ||
                (l(j) == c(s[i - 1]) && !lp(j)) ||
                (r(j) == c(s[i - 1]) && !rp(j))) {
                d[i][j] = p[i][j] = -1;
                continue;
            }
        }
    }
    stack<int> st;
    int ii = n, jj = -1;
    for (int j = 0; j < 64; j++)
        if (d[ii][j] != -1 && (jj == -1 || d[ii][j] < d[ii][jj]))
            jj = j;
    printf("%d\n", d[ii][jj]);
    while (ii) {
        st.push(jj);
        jj = p[ii--][jj];
    }
    char q[] = "LURD";
    while (!st.empty()) {
        printf("%c%c\n", q[l(st.top())], q[r(st.top())]);
        st.pop();
    }
    return 0;
}